diff --git a/CHANGELOG.md b/CHANGELOG.md
index e4dd817..50055df 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,6 +1,7 @@
 ## next
 
 - Added `repo.describeRef(ref)` method, which returns an information object about the reference
+- Added `repo.isOid(value)` method to check if a value is an object ID
 
 ## 0.1.3 (2023-10-13)
 
diff --git a/README.md b/README.md
index b72e8a7..52dd7ea 100644
--- a/README.md
+++ b/README.md
@@ -130,6 +130,14 @@ const info = repo.describeRef('origin/HEAD');
 //   oid: '7b84f676f2fbea2a3c6d83924fa63059c7bdfbe2'
 // }
 ```
+
+#### repo.isOid(value)
+
+Checks if a `value` is a valid oid.
+
+```js
+repo.isOid('7b84f676f2fbea2a3c6d83924fa63059c7bdfbe2'); // true
+repo.isOid('main'); // false
 ```
 
 #### repo.listRemotes()
diff --git a/src/resolve-ref.ts b/src/resolve-ref.ts
index bf03477..7081ce5 100644
--- a/src/resolve-ref.ts
+++ b/src/resolve-ref.ts
@@ -164,6 +164,7 @@ export async function createRefIndex(gitdir: string) {
         );
 
     return {
+        isOid,
         isRefExists: (ref: string) => expandRef(ref) !== null,
         resolveRef,
         expandRef: (ref: string) => (isOid(ref) ? ref : expandRef(ref)),
diff --git a/test/resolve-ref.ts b/test/resolve-ref.ts
index 1b3e57b..397bb2f 100644
--- a/test/resolve-ref.ts
+++ b/test/resolve-ref.ts
@@ -373,4 +373,24 @@ describe('resolve-ref', () => {
             });
         });
     });
+
+    describe('isOid()', () => {
+        it('should return true for a valid OID (40-character hexadecimal string)', function () {
+            assert.strictEqual(repo.isOid('1234567890abcdef1234567890abcdef12345678'), true);
+        });
+
+        const badValues = [
+            '1234567890abcdef1234567890abcdef1234',
+            '1234567890abcdef1234567890abcdef12345678901234',
+            '1234567890abcdef1234567890abcdef1234567G',
+            1234567895678901,
+            ''
+        ];
+
+        for (const value of badValues) {
+            it(JSON.stringify(value), () => {
+                assert.strictEqual(repo.isOid('1234567890abcdef1234567890abcdef1234567G'), false);
+            });
+        }
+    });
 });