diff --git a/compiler/ast/dag/expr.go b/compiler/ast/dag/expr.go
index a735d4133a..7fe4779afa 100644
--- a/compiler/ast/dag/expr.go
+++ b/compiler/ast/dag/expr.go
@@ -21,6 +21,11 @@ type (
 		Expr  Expr   `json:"expr"`
 		Where Expr   `json:"where"`
 	}
+	ApplyExpr struct {
+		Kind string `json:"kind" unpack:""`
+		Expr Expr   `json:"expr"`
+		Func string `json:"call"`
+	}
 	ArrayExpr struct {
 		Kind  string       `json:"kind" unpack:""`
 		Elems []VectorElem `json:"elems"`
@@ -113,6 +118,7 @@ type (
 )
 
 func (*Agg) ExprDAG()          {}
+func (*ApplyExpr) ExprDAG()    {}
 func (*ArrayExpr) ExprDAG()    {}
 func (*Assignment) ExprDAG()   {}
 func (*BinaryExpr) ExprDAG()   {}
diff --git a/compiler/ast/dag/unpack.go b/compiler/ast/dag/unpack.go
index 0a03034870..6ebdcf51fe 100644
--- a/compiler/ast/dag/unpack.go
+++ b/compiler/ast/dag/unpack.go
@@ -8,6 +8,7 @@ import (
 
 var unpacker = unpack.New(
 	Agg{},
+	ApplyExpr{},
 	ArrayExpr{},
 	Assignment{},
 	BinaryExpr{},
diff --git a/compiler/kernel/expr.go b/compiler/kernel/expr.go
index 80d5dae6d4..c03ef11450 100644
--- a/compiler/kernel/expr.go
+++ b/compiler/kernel/expr.go
@@ -91,6 +91,8 @@ func (b *Builder) compileExpr(e dag.Expr) (expr.Evaluator, error) {
 			return nil, err
 		}
 		return expr.NewAggregatorExpr(agg), nil
+	case *dag.ApplyExpr:
+		return b.compileApplyExpr(e)
 	case *dag.OverExpr:
 		return b.compileOverExpr(e)
 	default:
@@ -335,13 +337,9 @@ func (b *Builder) compileCall(call dag.Call) (expr.Evaluator, error) {
 	var path field.Path
 	// First check if call is to a user defined function, otherwise check for
 	// builtin function.
-	fn, ok := b.funcs[call.Name]
-	if !ok {
-		var err error
-		fn, path, err = function.New(b.zctx(), call.Name, len(call.Args))
-		if err != nil {
-			return nil, fmt.Errorf("%s(): %w", call.Name, err)
-		}
+	fn, err := b.lookupFunc(call.Name, len(call.Args))
+	if err != nil {
+		return nil, fmt.Errorf("internal error %s(): %w", call.Name, err)
 	}
 	args := call.Args
 	if path != nil {
@@ -355,6 +353,29 @@ func (b *Builder) compileCall(call dag.Call) (expr.Evaluator, error) {
 	return expr.NewCall(b.zctx(), fn, exprs), nil
 }
 
+func (b *Builder) lookupFunc(name string, nargs int) (expr.Function, error) {
+	fn, ok := b.funcs[name]
+	if !ok {
+		var err error
+		if fn, _, err = function.New(b.zctx(), name, nargs); err != nil {
+			return nil, err
+		}
+	}
+	return fn, nil
+}
+
+func (b *Builder) compileApplyExpr(a *dag.ApplyExpr) (expr.Evaluator, error) {
+	e, err := b.compileExpr(a.Expr)
+	if err != nil {
+		return nil, err
+	}
+	fn, err := b.lookupFunc(a.Func, 1)
+	if err != nil {
+		return nil, err
+	}
+	return expr.NewApplyFunc(b.zctx(), e, fn), nil
+}
+
 func (b *Builder) compileExprs(in []dag.Expr) ([]expr.Evaluator, error) {
 	var exprs []expr.Evaluator
 	for _, e := range in {
diff --git a/compiler/kernel/op.go b/compiler/kernel/op.go
index e51e960209..08353da86a 100644
--- a/compiler/kernel/op.go
+++ b/compiler/kernel/op.go
@@ -51,6 +51,7 @@ type Builder struct {
 	progress *zbuf.Progress
 	deletes  *sync.Map
 	funcs    map[string]expr.Function
+	funcArgs map[string]int
 }
 
 func NewBuilder(octx *op.Context, source *data.Source) *Builder {
diff --git a/compiler/semantic/expr.go b/compiler/semantic/expr.go
index 68c21341eb..dd88aad122 100644
--- a/compiler/semantic/expr.go
+++ b/compiler/semantic/expr.go
@@ -12,6 +12,7 @@ import (
 	"github.com/brimdata/zed/pkg/reglob"
 	"github.com/brimdata/zed/runtime/expr"
 	"github.com/brimdata/zed/runtime/expr/agg"
+	"github.com/brimdata/zed/runtime/expr/function"
 	"github.com/brimdata/zed/zson"
 )
 
@@ -473,26 +474,53 @@ func (a *analyzer) semCall(call *ast.Call) (dag.Expr, error) {
 	if err != nil {
 		return nil, fmt.Errorf("%s: bad argument: %w", call.Name, err)
 	}
+	err = a.validateFnCall(call.Name, len(exprs))
+	if errors.Is(err, function.ErrNoSuchFunction) && call.Name == "apply" {
+		if len(call.Args) != 2 {
+			return nil, fmt.Errorf("apply(): expects 2 argument(s)")
+		}
+		callid, ok := call.Args[1].(*ast.ID)
+		if !ok {
+			return nil, fmt.Errorf("apply(): second argument must be the identifier of a func")
+		}
+		if err := a.validateFnCall(callid.Name, 1); err != nil {
+			return nil, fmt.Errorf("%s(): %w", callid.Name, err)
+		}
+		return &dag.ApplyExpr{
+			Kind: "ApplyExpr",
+			Expr: exprs[0],
+			Func: callid.Name,
+		}, nil
+	}
+	if err != nil {
+		return nil, fmt.Errorf("%s(): %w", call.Name, err)
+	}
+	return &dag.Call{
+		Kind: "Call",
+		Name: call.Name,
+		Args: exprs,
+	}, nil
+}
+
+func (a *analyzer) validateFnCall(name string, nargs int) error {
 	// Call could be to a user defined func. Check if we have a matching func in
 	// scope.
-	e, err := a.scope.LookupExpr(call.Name)
+	e, err := a.scope.LookupExpr(name)
 	if err != nil {
-		return nil, err
+		return err
 	}
 	if e != nil {
 		f, ok := e.(*dag.Func)
 		if !ok {
-			return nil, fmt.Errorf("%s(): definition is not a function type: %T", call.Name, e)
+			return fmt.Errorf("definition is not a function type: %T", e)
 		}
-		if len(f.Params) != len(call.Args) {
-			return nil, fmt.Errorf("%s(): expects %d argument(s)", call.Name, len(f.Params))
+		if len(f.Params) != nargs {
+			return fmt.Errorf("expects %d argument(s)", len(f.Params))
 		}
+		return nil
 	}
-	return &dag.Call{
-		Kind: "Call",
-		Name: call.Name,
-		Args: exprs,
-	}, nil
+	_, _, err = function.New(a.zctx, name, nargs)
+	return err
 }
 
 func (a *analyzer) semExprs(in []ast.Expr) ([]dag.Expr, error) {
diff --git a/runtime/expr/apply.go b/runtime/expr/apply.go
new file mode 100644
index 0000000000..e7fa26d50c
--- /dev/null
+++ b/runtime/expr/apply.go
@@ -0,0 +1,66 @@
+package expr
+
+import (
+	"github.com/brimdata/zed"
+	"github.com/brimdata/zed/zcode"
+)
+
+type apply struct {
+	builder zcode.Builder
+	eval    Evaluator
+	fn      Function
+	zctx    *zed.Context
+
+	// vals is used to reduce allocations
+	vals []zed.Value
+	// types is used to reduce allocations
+	types []zed.Type
+}
+
+func NewApplyFunc(zctx *zed.Context, e Evaluator, fn Function) Evaluator {
+	return &apply{eval: e, fn: fn, zctx: zctx}
+}
+
+func (a *apply) Eval(ectx Context, in *zed.Value) *zed.Value {
+	v := a.eval.Eval(ectx, in)
+	if v.IsError() {
+		return v
+	}
+	elems, err := v.Elements()
+	if err != nil {
+		return ectx.CopyValue(*a.zctx.WrapError(err.Error(), in))
+	}
+	if len(elems) == 0 {
+		return v
+	}
+	a.vals = a.vals[:0]
+	a.types = a.types[:0]
+	for _, elem := range elems {
+		out := a.fn.Call(ectx, []zed.Value{elem})
+		a.vals = append(a.vals, *out)
+		a.types = append(a.types, out.Type)
+	}
+	inner := a.innerType(a.types)
+	a.builder.Reset()
+	if union, ok := inner.(*zed.TypeUnion); ok {
+		for _, val := range a.vals {
+			zed.BuildUnion(&a.builder, union.TagOf(val.Type), val.Bytes())
+		}
+	} else {
+		for _, val := range a.vals {
+			a.builder.Append(val.Bytes())
+		}
+	}
+	if _, ok := zed.TypeUnder(in.Type).(*zed.TypeSet); ok {
+		return ectx.NewValue(a.zctx.LookupTypeSet(inner), zed.NormalizeSet(a.builder.Bytes()))
+	}
+	return ectx.NewValue(a.zctx.LookupTypeArray(inner), a.builder.Bytes())
+}
+
+func (a *apply) innerType(types []zed.Type) zed.Type {
+	types = zed.UniqueTypes(types)
+	if len(types) == 1 {
+		return types[0]
+	}
+	return a.zctx.LookupTypeUnion(types)
+}
diff --git a/runtime/expr/ztests/apply.yaml b/runtime/expr/ztests/apply.yaml
new file mode 100644
index 0000000000..e564fbdc6c
--- /dev/null
+++ b/runtime/expr/ztests/apply.yaml
@@ -0,0 +1,7 @@
+script: |
+  echo '{a:["foo","bar","baz"]}' | zq -z 'a := apply(a,upper)' -
+
+outputs:
+  - name: stdout
+    data: |
+      {a:["FOO","BAR","BAZ"]}