diff --git a/doc/specs/stdlib_hashmaps.md b/doc/specs/stdlib_hashmaps.md
index 0fa8332fb..ea541d780 100644
--- a/doc/specs/stdlib_hashmaps.md
+++ b/doc/specs/stdlib_hashmaps.md
@@ -890,7 +890,10 @@ It also defines five non-overridable procedures:
 * `num_slots` - returns the number of slots in the map; and
 
 * `slots_bits` - returns the number of bits used to address the slots;
-and eleven deferred procedures:
+
+and ten deferred procedures:
+
+* `get_all_keys` - gets all the keys contained in a map;
 
 * `get_other_data` - gets the other map data associated with the key;
 
@@ -932,6 +935,7 @@ The type's definition is below:
         procedure, non_overridable, pass(map) :: map_probes
         procedure, non_overridable, pass(map) :: slots_bits
         procedure, non_overridable, pass(map) :: num_slots
+        procedure(get_all_keys), deferred, pass(map) :: get_all_keys
         procedure(get_other), deferred, pass(map)    :: get_other_data
         procedure(init_map), deferred, pass(map)     :: init
         procedure(key_test), deferred, pass(map)     :: key_test 
@@ -1026,6 +1030,7 @@ as follows:
         type(chaining_map_entry_ptr), allocatable :: inverse(:) 
         type(chaining_map_entry_ptr), allocatable :: slots(:)
     contains
+        procedure :: get_all_keys => get_all_chaining_keys
         procedure :: get_other_data => get_other_chaining_data
         procedure :: init => init_chaining_map
         procedure :: key => chaining_key_test 
@@ -1103,6 +1108,7 @@ as follows:
         type(open_map_entry_ptr), allocatable :: inverse(:)
         integer(int_index), allocatable       :: slots(:) 
     contains
+        procedure :: get_all_keys => get_all_open_keys
         procedure :: get_other_data => get_other_open_data
         procedure :: init => init_open_map
         procedure :: key_test => open_key_test 
@@ -1148,6 +1154,9 @@ Procedures to modify the content of a map:
 
 Procedures to report the content of a map:
 
+* `map % get_all_keys( all_keys )` - Returns all the keys
+  contained in the map;
+
 * `map % get_other_data( key, other, exists )` - Returns the other data
   associated with the `key`;
 
@@ -1251,6 +1260,41 @@ The result will be the number of entries in the hash map.
 ```
 
 
+#### `get_all_keys` - Returns all the keys contained in a map
+
+##### Status
+
+Experimental
+
+##### Description
+
+Returns all the keys contained in a map.
+
+##### Syntax
+
+`call map % [[hashmap_type(type):get_all_keys(bound)]]( all_keys )`
+
+##### Class
+
+Subroutine
+
+##### Arguments
+
+`map` (pass): shall be a scalar variable of class
+  `chaining_hashmap_type` or `open_hashmap_type`. It is an
+  `intent(in)` argument. It will be 
+  the hash map used to store and access the other data.
+
+`all_keys`: shall be a rank-1 allocatable array of type `key_type`. 
+  It is an `intent(out)` argument.
+
+##### Example
+
+```fortran
+{!example/hashmaps/example_hashmaps_get_all_keys.f90!}
+```
+
+
 #### `get_other_data` - Returns other data associated with the `key`
 
 ##### Status
diff --git a/example/hashmaps/CMakeLists.txt b/example/hashmaps/CMakeLists.txt
index c3962fcfb..fa97acd0a 100644
--- a/example/hashmaps/CMakeLists.txt
+++ b/example/hashmaps/CMakeLists.txt
@@ -8,6 +8,7 @@ ADD_EXAMPLE(hashmaps_fnv_1_hasher)
 ADD_EXAMPLE(hashmaps_free_key)
 ADD_EXAMPLE(hashmaps_free_other)
 ADD_EXAMPLE(hashmaps_get)
+ADD_EXAMPLE(hashmaps_get_all_keys)
 ADD_EXAMPLE(hashmaps_get_other_data)
 ADD_EXAMPLE(hashmaps_hasher_fun)
 ADD_EXAMPLE(hashmaps_init)
diff --git a/example/hashmaps/example_hashmaps_get_all_keys.f90 b/example/hashmaps/example_hashmaps_get_all_keys.f90
new file mode 100644
index 000000000..2188fb181
--- /dev/null
+++ b/example/hashmaps/example_hashmaps_get_all_keys.f90
@@ -0,0 +1,52 @@
+program example_hashmaps_get_all_keys
+  use stdlib_kinds, only: int32
+  use stdlib_hashmaps, only: chaining_hashmap_type
+  use stdlib_hashmap_wrappers, only: fnv_1_hasher, &
+                                     key_type, other_type, set
+  implicit none
+  type(chaining_hashmap_type) :: map
+  type(key_type)   :: key
+  type(other_type) :: other
+
+  type(key_type), allocatable :: keys(:)
+  integer(int32) :: i
+
+  call map%init(fnv_1_hasher)
+
+  ! adding key-value pairs to the map
+  call set(key, "initial key")
+  call set(other, "value 1")
+  call map%map_entry(key, other)
+
+  call set(key, "second key")
+  call set(other, "value 2")
+  call map%map_entry(key, other)
+
+  call set(key, "last key")
+  call set(other, "value 3")
+  call map%map_entry(key, other)
+
+  ! getting all the keys in the map
+  call map%get_all_keys(keys)
+
+  print '("Number of keys in the hashmap = ", I0)', size(keys)
+  !Number of keys in the hashmap = 3
+
+  do i = 1, size(keys)
+    print '("Value of key ", I0, " = ", A)', i, key_to_char(keys(i))
+  end do
+  !Value of key 1 = initial key
+  !Value of key 2 = second key
+  !Value of key 3 = last key
+
+contains
+  !Converts key type to character type
+  pure function key_to_char(key) result(str)
+    type(key_type), intent(in) :: key
+    character(:), allocatable :: str
+    character(:), allocatable :: str_mold
+
+    allocate( character(len=size(key%value)) :: str_mold )
+    str = transfer(key%value, str_mold)
+  end function key_to_char
+end program example_hashmaps_get_all_keys
diff --git a/src/stdlib_hashmap_chaining.f90 b/src/stdlib_hashmap_chaining.f90
index 7db08861a..273545680 100755
--- a/src/stdlib_hashmap_chaining.f90
+++ b/src/stdlib_hashmap_chaining.f90
@@ -284,6 +284,37 @@ recursive subroutine free_map_entry_pool(pool) ! gent_pool_free
     end subroutine free_map_entry_pool
 
 
+    module subroutine get_all_chaining_keys(map, all_keys)
+!! Version: Experimental
+!!
+!! Returns all the keys contained in a hash map
+!! Arguments:
+!!     map - a chaining hash map
+!!     all_keys - all the keys contained in a hash map
+!
+        class(chaining_hashmap_type), intent(in) :: map
+        type(key_type), allocatable, intent(out) :: all_keys(:)
+        
+        integer(int32) :: num_keys
+        integer(int_index) :: i, key_idx
+
+        num_keys = map % entries()
+        allocate( all_keys(num_keys) )
+        if ( num_keys == 0 ) return
+
+        if( allocated( map % inverse ) ) then
+            key_idx = 1_int_index
+            do i=1_int_index, size( map % inverse, kind=int_index )
+                if ( associated( map % inverse(i) % target ) ) then
+                    all_keys(key_idx) = map % inverse(i) % target % key
+                    key_idx = key_idx + 1_int_index
+                end if
+            end do 
+        end if
+
+    end subroutine get_all_chaining_keys
+
+
     module subroutine get_other_chaining_data( map, key, other, exists )
 !! Version: Experimental
 !!
diff --git a/src/stdlib_hashmap_open.f90 b/src/stdlib_hashmap_open.f90
index 979b097e9..b271f9869 100755
--- a/src/stdlib_hashmap_open.f90
+++ b/src/stdlib_hashmap_open.f90
@@ -254,6 +254,37 @@ module subroutine free_open_map( map )
     end subroutine free_open_map
 
 
+    module subroutine get_all_open_keys(map, all_keys)
+!! Version: Experimental
+!!
+!! Returns all the keys contained in a hash map
+!! Arguments:
+!!     map - an open hash map
+!!     all_keys - all the keys contained in a hash map
+!
+        class(open_hashmap_type), intent(in) :: map
+        type(key_type), allocatable, intent(out) :: all_keys(:)
+        
+        integer(int32) :: num_keys
+        integer(int_index) :: i, key_idx
+
+        num_keys = map % entries()
+        allocate( all_keys(num_keys) )
+        if ( num_keys == 0 ) return
+
+        if ( allocated( map % inverse) ) then
+            key_idx = 1_int_index
+            do i=1_int_index, size( map % inverse, kind=int_index )
+                if ( associated( map % inverse(i) % target ) ) then
+                    all_keys(key_idx) = map % inverse(i) % target % key
+                    key_idx = key_idx + 1_int_index
+                end if
+            end do 
+        end if
+
+    end subroutine get_all_open_keys
+
+
     module subroutine get_other_open_data( map, key, other, exists )
 !! Version: Experimental
 !!
diff --git a/src/stdlib_hashmaps.f90 b/src/stdlib_hashmaps.f90
index f7f29c683..4b3044583 100644
--- a/src/stdlib_hashmaps.f90
+++ b/src/stdlib_hashmaps.f90
@@ -94,6 +94,7 @@ module stdlib_hashmaps
         procedure, non_overridable, pass(map) :: map_probes
         procedure, non_overridable, pass(map) :: num_slots
         procedure, non_overridable, pass(map) :: slots_bits
+        procedure(get_all_keys), deferred, pass(map) :: get_all_keys
         procedure(get_other), deferred, pass(map)    :: get_other_data
         procedure(init_map), deferred, pass(map)     :: init
         procedure(key_test), deferred, pass(map)     :: key_test
@@ -109,6 +110,21 @@ module stdlib_hashmaps
 
     abstract interface
 
+        subroutine get_all_keys(map, all_keys)
+!! Version: Experimental
+!!
+!! Returns the all keys contained in a hash map
+!! ([Specifications](../page/specs/stdlib_hashmaps.html#get_all_keys-returns-all-the-keys-contained-in-a-map))
+!!
+!! Arguments:
+!!     map - a hash map
+!!     all_keys - all the keys contained in a hash map
+!
+            import hashmap_type, key_type
+            class(hashmap_type), intent(in) :: map
+            type(key_type), allocatable, intent(out) :: all_keys(:)
+        end subroutine get_all_keys
+
         subroutine get_other( map, key, other, exists )
 !! Version: Experimental
 !!
@@ -319,6 +335,7 @@ end function total_depth
         type(chaining_map_entry_ptr), allocatable :: slots(:)
 !! Array of bucket lists Note # slots=size(slots)
     contains
+        procedure :: get_all_keys => get_all_chaining_keys
         procedure :: get_other_data => get_other_chaining_data
         procedure :: init => init_chaining_map
         procedure :: loading => chaining_loading
@@ -345,6 +362,19 @@ module subroutine free_chaining_map( map )
         end subroutine free_chaining_map
 
 
+        module subroutine get_all_chaining_keys(map, all_keys)
+!! Version: Experimental
+!!
+!! Returns all the keys contained in a hashmap
+!! Arguments:
+!!     map - an chaining hash map
+!!     all_keys - all the keys contained in a hash map
+!
+            class(chaining_hashmap_type), intent(in) :: map
+            type(key_type), allocatable, intent(out) :: all_keys(:)
+        end subroutine get_all_chaining_keys
+
+
         module subroutine get_other_chaining_data( map, key, other, exists )
 !! Version: Experimental
 !!
@@ -556,6 +586,7 @@ end function total_chaining_depth
         integer(int_index), allocatable        :: slots(:)
 !! Array of indices to the inverse Note # slots=size(slots)
     contains
+        procedure :: get_all_keys => get_all_open_keys
         procedure :: get_other_data => get_other_open_data
         procedure :: init => init_open_map
         procedure :: loading => open_loading
@@ -581,6 +612,19 @@ module subroutine free_open_map( map )
         end subroutine free_open_map
 
 
+        module subroutine get_all_open_keys(map, all_keys)
+!! Version: Experimental
+!!
+!! Returns all the keys contained in a hashmap
+!! Arguments:
+!!     map - an open hash map
+!!     all_keys - all the keys contained in a hash map
+!
+            class(open_hashmap_type), intent(in) :: map
+            type(key_type), allocatable, intent(out) :: all_keys(:)
+        end subroutine get_all_open_keys
+
+
         module subroutine get_other_open_data( map, key, other, exists )
 !! Version: Experimental
 !!
diff --git a/test/hashmaps/test_chaining_maps.f90 b/test/hashmaps/test_chaining_maps.f90
index d63346e3d..13d062118 100755
--- a/test/hashmaps/test_chaining_maps.f90
+++ b/test/hashmaps/test_chaining_maps.f90
@@ -51,6 +51,7 @@ program test_chaining_maps
     call map % init( fnv_1_hasher, slots_bits=10 )
     call input_random_data( map, test_16, 'FNV-1', "16 byte words" )
     call test_inquire_data( map, test_16, 'FNV-1', "16 byte words" )
+    call test_get_all_keys( map, test_16, 'FNV-1', '16 byte words' )
     call test_get_data( map, test_16, 'FNV-1', '16 byte words' )
     call report_rehash_times( map, fnv_1_hasher, 'FNV-1', '16 byte words' )
     call report_hash_statistics( map, 'FNV-1', '16 byte words' )
@@ -60,6 +61,7 @@ program test_chaining_maps
     call input_random_data( map, test_256, 'FNV-1', "256 byte words" )
     call test_inquire_data( map, test_256, 'FNV-1', "256 byte words" )
     call test_get_data( map, test_256, 'FNV-1', '256 byte words' )
+    call test_get_all_keys( map, test_256, 'FNV-1', '256 byte words' )
     call report_rehash_times( map, fnv_1_hasher, 'FNV-1', '256 byte words' )
     call report_hash_statistics( map, 'FNV-1', '256 byte words' )
     call report_removal_times( map, test_256, 'FNV-1', '256 byte words' )
@@ -68,6 +70,7 @@ program test_chaining_maps
     call input_random_data( map, test_16, 'FNV-1A', "16 byte words" )
     call test_inquire_data( map, test_16, 'FNV-1A', "16 byte words" )
     call test_get_data( map, test_16, 'FNV-1A', '16 byte words' )
+    call test_get_all_keys( map, test_16, 'FNV-1A', '16 byte words' )
     call report_rehash_times( map, fnv_1a_hasher, 'FNV-1', '16 byte words' )
     call report_hash_statistics( map, 'FNV-1A', '16 byte words' )
     call report_removal_times( map, test_16, 'FNV-1a', '16 byte words' )
@@ -76,6 +79,7 @@ program test_chaining_maps
     call input_random_data( map, test_256, 'FNV-1A', "256 byte words" )
     call test_inquire_data( map, test_256, 'FNV-1A', "256 byte words" )
     call test_get_data( map, test_256, 'FNV-1A', '256 byte words' )
+    call test_get_all_keys( map, test_256, 'FNV-1A', '256 byte words' )
     call report_rehash_times( map, fnv_1_hasher, 'FNV-1A', '256 byte words' )
     call report_hash_statistics( map, 'FNV-1A', '256 byte words' )
     call report_removal_times( map, test_256, 'FNV-1A', '256 byte words' )
@@ -84,6 +88,7 @@ program test_chaining_maps
     call input_random_data( map, test_16, 'Seeded_Nmhash32', "16 byte words" )
     call test_inquire_data( map, test_16, 'Seeded_Nmhash32', "16 byte words" )
     call test_get_data( map, test_16, 'Seeded_Nmhash32', '16 byte words' )
+    call test_get_all_keys( map, test_16, 'Seeded_Nmhash32', '16 byte words' )
     call report_rehash_times( map, seeded_nmhash32_hasher, 'Seeded_Nmhash32', &
         '16 byte words' )
     call report_hash_statistics( map, 'Seeded_Nmhash32', '16 byte words' )
@@ -94,6 +99,7 @@ program test_chaining_maps
     call input_random_data( map, test_256, 'Seeded_Nmhash32', "256 byte words" )
     call test_inquire_data( map, test_256, 'Seeded_Nmhash32', "256 byte words" )
     call test_get_data( map, test_256, 'Seeded_Nmhash32', '256 byte words' )
+    call test_get_all_keys( map, test_256, 'Seeded_Nmhash32', '256 byte words' )
     call report_rehash_times( map, seeded_nmhash32_hasher, 'Seeded_Nmhash32', &
         '256 byte words' )
     call report_hash_statistics( map, 'Seeded_Nmhash32', '256 byte words' )
@@ -104,6 +110,7 @@ program test_chaining_maps
     call input_random_data( map, test_16, 'Seeded_Nmhash32x', "16 byte words" )
     call test_inquire_data( map, test_16, 'Seeded_Nmhash32x', "16 byte words" )
     call test_get_data( map, test_16, 'Seeded_Nmhash32x', '16 byte words' )
+    call test_get_all_keys( map, test_16, 'Seeded_Nmhash32x', '16 byte words' )
     call report_rehash_times( map, seeded_nmhash32x_hasher, &
         'Seeded_Nmhash32x', '16 byte words' )
     call report_hash_statistics( map, 'Seeded_Nmhash32x', '16 byte words' )
@@ -116,6 +123,7 @@ program test_chaining_maps
     call test_inquire_data( map, test_256, 'Seeded_Nmhash32x', &
         "256 byte words" )
     call test_get_data( map, test_256, 'Seeded_Nmhash32x', '256 byte words' )
+    call test_get_all_keys( map, test_256, 'Seeded_Nmhash32x', '256 byte words' )
     call report_rehash_times( map, seeded_nmhash32x_hasher, &
         'Seeded_Nmhash32x', '256 byte words' )
     call report_hash_statistics( map, 'Seeded_Nmhash32x', '256 byte words' )
@@ -126,6 +134,7 @@ program test_chaining_maps
     call input_random_data( map, test_16, 'Seeded_Water', "16 byte words" )
     call test_inquire_data( map, test_16, 'Seeded_Water', "16 byte words" )
     call test_get_data( map, test_16, 'Seeded_Water', '16 byte words' )
+    call test_get_all_keys( map, test_16, 'Seeded_Water', '16 byte words' )
     call report_rehash_times( map, seeded_water_hasher, &
         'Seeded_Water', '16 byte words' )
     call report_hash_statistics( map, 'Seeded_Water', '16 byte words' )
@@ -138,6 +147,7 @@ program test_chaining_maps
     call test_inquire_data( map, test_256, 'Seeded_Water', &
         "256 byte words" )
     call test_get_data( map, test_256, 'Seeded_Water', '256 byte words' )
+    call test_get_all_keys( map, test_256, 'Seeded_Water', '256 byte words' )
     call report_rehash_times( map, seeded_water_hasher, &
         'Seeded_Water', '256 byte words' )
     call report_hash_statistics( map, 'Seeded_Water', '256 byte words' )
@@ -227,6 +237,37 @@ subroutine test_get_data( map, test_block, hash_name, size_name )
     end subroutine test_get_data
 
 
+    subroutine test_get_all_keys( map, test_block, hash_name, size_name )
+        type(chaining_hashmap_type), intent(inout) :: map
+        integer(int_index), intent(in)          :: test_block
+        character(*), intent(in)                :: hash_name, size_name
+        integer :: index2, key_idx
+        type(key_type) :: key
+        type(key_type), allocatable :: all_keys(:)
+        real :: t1, t2, tdiff
+
+        call cpu_time(t1)
+        call map % get_all_keys(all_keys)
+        call cpu_time(t2)
+        tdiff = t2-t1
+
+        if (size( all_keys ) /= size( test_8_bits )/test_block) &
+            error stop "Number of keys is different from that of keys in a map."
+
+        do index2=1, size(test_8_bits), test_block
+            call set( key, test_8_bits( index2:index2+test_block-1 ) )
+
+            key_idx = ( index2/test_block ) + 1
+            if (.not. ( all_keys(key_idx) == key )) &
+                error stop "Invalid value of a key."
+        end do
+
+        write(lun, '("|", a18, " | ", a12, " | ", a15, " | ", f10.5, " |")') &
+            trim(hash_name), 'Get all keys', size_name, tdiff
+
+    end subroutine test_get_all_keys
+
+
     subroutine report_rehash_times( map, hasher, hash_name, size_name )
         type(chaining_hashmap_type), intent(inout) :: map
         procedure(hasher_fun)                   :: hasher
diff --git a/test/hashmaps/test_open_maps.f90 b/test/hashmaps/test_open_maps.f90
index d569d238c..7e1ff9764 100755
--- a/test/hashmaps/test_open_maps.f90
+++ b/test/hashmaps/test_open_maps.f90
@@ -53,6 +53,7 @@ program test_open_maps
     call input_random_data( map, test_16, 'FNV-1', "16 byte words" )
     call test_inquire_data( map, test_16, 'FNV-1', "16 byte words" )
     call test_get_data( map, test_16, 'FNV-1', '16 byte words' )
+    call test_get_all_keys( map, test_16, 'FNV-1', '16 byte words' )
     call report_rehash_times( map, fnv_1_hasher, 'FNV-1', '16 byte words' )
     call report_hash_statistics( map, 'FNV-1', '16 byte words' )
     call report_removal_times( map, test_16, 'FNV-1', '16 byte words' )
@@ -61,6 +62,7 @@ program test_open_maps
     call input_random_data( map, test_256, 'FNV-1', "256 byte words" )
     call test_inquire_data( map, test_256, 'FNV-1', "256 byte words" )
     call test_get_data( map, test_256, 'FNV-1', '256 byte words' )
+    call test_get_all_keys( map, test_256, 'FNV-1', '256 byte words' )
     call report_rehash_times( map, fnv_1_hasher, 'FNV-1', '256 byte words' )
     call report_hash_statistics( map, 'FNV-1', '256 byte words' )
     call report_removal_times( map, test_256, 'FNV-1', '256 byte words' )
@@ -69,6 +71,7 @@ program test_open_maps
     call input_random_data( map, test_16, 'FNV-1A', "16 byte words" )
     call test_inquire_data( map, test_16, 'FNV-1A', "16 byte words" )
     call test_get_data( map, test_16, 'FNV-1A', '16 byte words' )
+    call test_get_all_keys( map, test_16, 'FNV-1A', '16 byte words' )
     call report_rehash_times( map, fnv_1a_hasher, 'FNV-1', '16 byte words' )
     call report_hash_statistics( map, 'FNV-1A', '16 byte words' )
     call report_removal_times( map, test_16, 'FNV-1a', '16 byte words' )
@@ -77,6 +80,7 @@ program test_open_maps
     call input_random_data( map, test_256, 'FNV-1A', "256 byte words" )
     call test_inquire_data( map, test_256, 'FNV-1A', "256 byte words" )
     call test_get_data( map, test_256, 'FNV-1A', '256 byte words' )
+    call test_get_all_keys( map, test_256, 'FNV-1A', '256 byte words' )
     call report_rehash_times( map, fnv_1_hasher, 'FNV-1A', '256 byte words' )
     call report_hash_statistics( map, 'FNV-1A', '256 byte words' )
     call report_removal_times( map, test_256, 'FNV-1A', '256 byte words' )
@@ -85,6 +89,7 @@ program test_open_maps
     call input_random_data( map, test_16, 'Seeded_Nmhash32', "16 byte words" )
     call test_inquire_data( map, test_16, 'Seeded_Nmhash32', "16 byte words" )
     call test_get_data( map, test_16, 'Seeded_Nmhash32', '16 byte words' )
+    call test_get_all_keys( map, test_16, 'Seeded_Nmhash32', '16 byte words' )
     call report_rehash_times( map, seeded_nmhash32_hasher, 'Seeded_Nmhash32', &
         '16 byte words' )
     call report_hash_statistics( map, 'Seeded_Nmhash32', '16 byte words' )
@@ -95,6 +100,7 @@ program test_open_maps
     call input_random_data( map, test_256, 'Seeded_Nmhash32', "256 byte words" )
     call test_inquire_data( map, test_256, 'Seeded_Nmhash32', "256 byte words" )
     call test_get_data( map, test_256, 'Seeded_Nmhash32', '256 byte words' )
+    call test_get_all_keys( map, test_256, 'Seeded_Nmhash32', '256 byte words' )
     call report_rehash_times( map, seeded_nmhash32_hasher, 'Seeded_Nmhash32', &
         '256 byte words' )
     call report_hash_statistics( map, 'Seeded_Nmhash32', '256 byte words' )
@@ -105,6 +111,7 @@ program test_open_maps
     call input_random_data( map, test_16, 'Seeded_Nmhash32x', "16 byte words" )
     call test_inquire_data( map, test_16, 'Seeded_Nmhash32x', "16 byte words" )
     call test_get_data( map, test_16, 'Seeded_Nmhash32x', '16 byte words' )
+    call test_get_all_keys( map, test_16, 'Seeded_Nmhash32x', '16 byte words' )
     call report_rehash_times( map, seeded_nmhash32x_hasher, &
         'Seeded_Nmhash32x', '16 byte words' )
     call report_hash_statistics( map, 'Seeded_Nmhash32x', '16 byte words' )
@@ -117,6 +124,7 @@ program test_open_maps
     call test_inquire_data( map, test_256, 'Seeded_Nmhash32x', &
         "256 byte words" )
     call test_get_data( map, test_256, 'Seeded_Nmhash32x', '256 byte words' )
+    call test_get_all_keys( map, test_256, 'Seeded_Nmhash32x', '256 byte words' )
     call report_rehash_times( map, seeded_nmhash32x_hasher, &
         'Seeded_Nmhash32x', '256 byte words' )
     call report_hash_statistics( map, 'Seeded_Nmhash32x', '256 byte words' )
@@ -127,6 +135,7 @@ program test_open_maps
     call input_random_data( map, test_16, 'Seeded_Water', "16 byte words" )
     call test_inquire_data( map, test_16, 'Seeded_Water', "16 byte words" )
     call test_get_data( map, test_16, 'Seeded_Water', '16 byte words' )
+    call test_get_all_keys( map, test_16, 'Seeded_Water', '16 byte words' )
     call report_rehash_times( map, seeded_water_hasher, &
         'Seeded_Water', '16 byte words' )
     call report_hash_statistics( map, 'Seeded_Water', '16 byte words' )
@@ -139,6 +148,7 @@ program test_open_maps
     call test_inquire_data( map, test_256, 'Seeded_Water', &
         "256 byte words" )
     call test_get_data( map, test_256, 'Seeded_Water', '256 byte words' )
+    call test_get_all_keys( map, test_256, 'Seeded_Water', '256 byte words' )
     call report_rehash_times( map, seeded_water_hasher, &
         'Seeded_Water', '256 byte words' )
     call report_hash_statistics( map, 'Seeded_Water', '256 byte words' )
@@ -228,6 +238,37 @@ subroutine test_get_data( map, test_block, hash_name, size_name )
     end subroutine test_get_data
 
 
+    subroutine test_get_all_keys( map, test_block, hash_name, size_name )
+        type(open_hashmap_type), intent(inout) :: map
+        integer(int_index), intent(in)          :: test_block
+        character(*), intent(in)                :: hash_name, size_name
+        integer :: index2, key_idx
+        type(key_type) :: key
+        type(key_type), allocatable :: all_keys(:)
+        real :: t1, t2, tdiff
+
+        call cpu_time(t1)
+        call map % get_all_keys(all_keys)
+        call cpu_time(t2)
+        tdiff = t2-t1
+
+        if (size( all_keys ) /= size( test_8_bits )/test_block) &
+            error stop "Number of keys is different from that of keys in a map."
+
+        do index2=1, size(test_8_bits), test_block
+            call set( key, test_8_bits( index2:index2+test_block-1 ) )
+
+            key_idx = ( index2/test_block ) + 1
+            if (.not. ( all_keys(key_idx) == key )) &
+                error stop "Invalid value of a key."
+        end do
+
+        write(lun, '("|", a18, " | ", a12, " | ", a15, " | ", f10.5, " |")') &
+            trim(hash_name), 'Get all keys', size_name, tdiff
+
+    end subroutine test_get_all_keys
+
+
     subroutine report_rehash_times( map, hasher, hash_name, size_name )
         type(open_hashmap_type), intent(inout) :: map
         procedure(hasher_fun)                   :: hasher