diff --git a/internal/ast/compiler/add_enum_value.go b/internal/ast/compiler/add_enum_value.go
new file mode 100644
index 000000000..a0cba81c7
--- /dev/null
+++ b/internal/ast/compiler/add_enum_value.go
@@ -0,0 +1,105 @@
+package compiler
+
+import (
+	"errors"
+
+	"github.com/grafana/cog/internal/ast"
+)
+
+type AddEnumValue struct {
+	ObjectRef ObjectReference
+	FieldRef  FieldReference
+	Name      string
+	Value     any
+}
+
+func (pass *AddEnumValue) Process(schemas []*ast.Schema) ([]*ast.Schema, error) {
+	if pass.Name == "" || pass.Value == nil {
+		return nil, errors.New("name and value are required")
+	}
+
+	visitor := &Visitor{
+		OnObject: pass.onObject,
+		OnEnum:   pass.onEnum,
+	}
+	return visitor.VisitSchemas(schemas)
+}
+
+func (pass *AddEnumValue) onObject(visitor *Visitor, schema *ast.Schema, object ast.Object) (ast.Object, error) {
+	if object.Type.IsEnum() && pass.ObjectRef.Matches(object) {
+		enum, err := visitor.OnEnum(visitor, schema, object.Type)
+		if err != nil {
+			return ast.Object{}, err
+		}
+
+		object.Type = enum
+		object.AddToPassesTrail("AddEnumValue")
+		return object, nil
+	}
+
+	if !object.Type.IsStruct() {
+		return object, nil
+	}
+
+	for i, field := range object.Type.AsStruct().Fields {
+		if pass.FieldRef.Matches(object, field) {
+			if field.Type.IsEnum() {
+				updatedType, err := visitor.OnEnum(visitor, schema, field.Type)
+				if err != nil {
+					return ast.Object{}, err
+				}
+				object.Type.AsStruct().Fields[i].Type = updatedType
+				object.Type.AsStruct().Fields[i].AddToPassesTrail("AddEnumValue")
+				return object, nil
+			}
+
+			if field.Type.IsRef() {
+				if enum, ok := pass.updateEnumObject(visitor, schema, field.Type); ok {
+					schema.Objects.Set(object.Name, enum)
+				}
+				return object, nil
+			}
+		}
+	}
+
+	return object, nil
+}
+
+func (pass *AddEnumValue) onEnum(_ *Visitor, _ *ast.Schema, def ast.Type) (ast.Type, error) {
+	enumString := def.AsEnum().Values[0].Type.AsScalar().ScalarKind == ast.KindString
+	_, isString := pass.Value.(string)
+
+	if enumString && !isString {
+		return ast.Type{}, errors.New("enum value must be of type string")
+	}
+	if !enumString && isString {
+		return ast.Type{}, errors.New("enum value must be of type integer")
+	}
+
+	def.Enum.Values = append(def.Enum.Values, ast.EnumValue{
+		Name:  pass.Name,
+		Type:  def.AsEnum().Values[0].Type,
+		Value: pass.Value,
+	})
+
+	return def, nil
+}
+
+func (pass *AddEnumValue) updateEnumObject(visitor *Visitor, schema *ast.Schema, def ast.Type) (ast.Object, bool) {
+	obj, ok := schema.LocateObject(def.AsRef().ReferredType)
+	if !ok {
+		return ast.Object{}, false
+	}
+
+	if !obj.Type.IsEnum() {
+		return ast.Object{}, false
+	}
+
+	enum, err := visitor.OnEnum(visitor, schema, obj.Type)
+	if err != nil {
+		return ast.Object{}, false
+	}
+
+	obj.Type = enum
+	return obj, true
+}
diff --git a/internal/ast/compiler/add_enum_value_test.go b/internal/ast/compiler/add_enum_value_test.go
new file mode 100644
index 000000000..0a69a166b
--- /dev/null
+++ b/internal/ast/compiler/add_enum_value_test.go
@@ -0,0 +1,144 @@
+package compiler
+
+import (
+	"testing"
+
+	"github.com/grafana/cog/internal/ast"
+	"github.com/grafana/cog/internal/testutils"
+	"github.com/stretchr/testify/require"
+)
+
+func TestAddEnumFieldValueReference(t *testing.T) {
+	schema := &ast.Schema{
+		Package: "add_enum_value",
+		Objects: testutils.ObjectsMap(
+			ast.NewObject("test", "MyEnum", ast.NewEnum([]ast.EnumValue{
+				{Value: "A", Name: "A", Type: ast.String()},
+				{Value: "B", Name: "B", Type: ast.String()},
+			})),
+			ast.NewObject("test", "MyStruct", ast.NewStruct(
+				ast.NewStructField("enum", ast.NewRef("test", "MyEnum")),
+			)),
+		),
+	}
+
+	expected := &ast.Schema{
+		Package: "add_enum_value",
+		Objects: testutils.ObjectsMap(
+			ast.NewObject("test", "MyEnum", ast.NewEnum([]ast.EnumValue{
+				{Value: "A", Name: "A", Type: ast.String()},
+				{Value: "B", Name: "B", Type: ast.String()},
+				{Value: "C", Name: "C", Type: ast.String()},
+			})),
+			ast.NewObject("test", "MyStruct", ast.NewStruct(
+				ast.NewStructField("enum", ast.NewRef("test", "MyEnum")),
+			)),
+		),
+	}
+
+	pass := &AddEnumValue{
+		FieldRef: FieldReference{
+			Package: "test",
+			Object:  "MyStruct",
+			Field:   "enum",
+		},
+		Name:  "C",
+		Value: "C",
+	}
+
+	runPassOnSchema(t, pass, schema, expected)
+}
+
+func TestAddEnumFieldValueDirectEnum(t *testing.T) {
+	schema := &ast.Schema{
+		Package: "add_enum_value",
+		Objects: testutils.ObjectsMap(
+			ast.NewObject("test", "MyStruct", ast.NewStruct(
+				ast.NewStructField("enum", ast.NewEnum([]ast.EnumValue{
+					{Value: 1, Name: "A", Type: ast.NewScalar(ast.KindInt64)},
+					{Value: 2, Name: "B", Type: ast.NewScalar(ast.KindInt64)},
+				})),
+			)),
+		),
+	}
+
+	expected := &ast.Schema{
+		Package: "add_enum_value",
+		Objects: testutils.ObjectsMap(
+			ast.NewObject("test", "MyStruct", ast.NewStruct(
+				ast.NewStructField("enum", ast.NewEnum([]ast.EnumValue{
+					{Value: 1, Name: "A", Type: ast.NewScalar(ast.KindInt64)},
+					{Value: 2, Name: "B", Type: ast.NewScalar(ast.KindInt64)},
+					{Value: 3, Name: "C", Type: ast.NewScalar(ast.KindInt64)},
+				}), ast.PassesTrail("AddEnumValue")),
+			)),
+		),
+	}
+
+	pass := &AddEnumValue{
+		FieldRef: FieldReference{
+			Package: "test",
+			Object:  "MyStruct",
+			Field:   "enum",
+		},
+		Name:  "C",
+		Value: 3,
+	}
+
+	runPassOnSchema(t, pass, schema, expected)
+}
+
+func TestAddEnumValueEnum(t *testing.T) {
+	schema := &ast.Schema{
+		Package: "add_enum_value",
+		Objects: testutils.ObjectsMap(ast.NewObject("test", "MyEnum", ast.NewEnum([]ast.EnumValue{
+			{Value: "A", Name: "A", Type: ast.String()},
+			{Value: "B", Name: "B", Type: ast.String()},
+		})),
+		),
+	}
+
+	expected := &ast.Schema{
+		Package: "add_enum_value",
+		Objects: testutils.ObjectsMap(ast.NewObject("test", "MyEnum", ast.NewEnum([]ast.EnumValue{
+			{Value: "A", Name: "A", Type: ast.String()},
+			{Value: "B", Name: "B", Type: ast.String()},
+			{Value: "C", Name: "C", Type: ast.String()},
+		}), "AddEnumValue"),
+		),
+	}
+
+	pass := &AddEnumValue{
+		ObjectRef: ObjectReference{
+			Package: "test",
+			Object:  "MyEnum",
+		},
+		Name:  "C",
+		Value: "C",
+	}
+
+	runPassOnSchema(t, pass, schema, expected)
+}
+
+func TestAddEnumValueInvalidValueKind(t *testing.T) {
+	schema := &ast.Schema{
+		Package: "add_enum_value",
+		Objects: testutils.ObjectsMap(ast.NewObject("test", "MyEnum", ast.NewEnum([]ast.EnumValue{
+			{Value: "A", Name: "A", Type: ast.String()},
+			{Value: "B", Name: "B", Type: ast.String()},
+		})),
+		),
+	}
+
+	pass := &AddEnumValue{
+		ObjectRef: ObjectReference{
+			Package: "test",
+			Object:  "MyEnum",
+		},
+		Name:  "C",
+		Value: 1,
+	}
+
+	_, err := pass.Process(ast.Schemas{schema})
+	require.Error(t, err)
+}
diff --git a/internal/yaml/compilerpasses.go b/internal/yaml/compilerpasses.go
index b14aa6c1d..71fe78ac1 100644
--- a/internal/yaml/compilerpasses.go
+++ b/internal/yaml/compilerpasses.go
@@ -29,6 +29,7 @@ type CompilerPass struct {
 	DuplicateObject          *DuplicateObject          `yaml:"duplicate_object"`
 	TrimEnumValues           *TrimEnumValues           `yaml:"trim_enum_values"`
 	ConstantToEnum           *ConstantToEnum           `yaml:"constant_to_enum"`
+	AddEnumValue             *AddEnumValue             `yaml:"add_enum_value"`
 
 	AnonymousStructsToNamed *AnonymousStructsToNamed `yaml:"anonymous_structs_to_named"`
 
@@ -119,6 +120,9 @@ func (pass CompilerPass) AsCompilerPass() (compiler.Pass, error) {
 	if pass.DisjunctionWithConstantToDefault != nil {
 		return pass.DisjunctionWithConstantToDefault.AsCompilerPass()
 	}
+	if pass.AddEnumValue != nil {
+		return pass.AddEnumValue.AsCompilerPass()
+	}
 
 	return nil, fmt.Errorf("empty compiler pass")
 }
@@ -494,3 +498,38 @@ func (pass ConstantToEnum) AsCompilerPass() (*compiler.ConstantToEnum, error) {
 
 	return &compiler.ConstantToEnum{Objects: objectRefs}, nil
 }
+
+type AddEnumValue struct {
+	Enum  string // Expected format: [package].[object]
+	Field string // Expected format: [package].[object].[field]
+	Name  string
+	Value any
+}
+
+func (pass AddEnumValue) AsCompilerPass() (*compiler.AddEnumValue, error) {
+	if pass.Enum != "" {
+		objectRef, err := compiler.ObjectReferenceFromString(pass.Enum)
+		if err != nil {
+			return nil, err
+		}
+
+		return &compiler.AddEnumValue{
+			ObjectRef: objectRef,
+			FieldRef:  compiler.FieldReference{},
+			Name:      pass.Name,
+			Value:     pass.Value,
+		}, nil
+	}
+
+	fieldRef, err := compiler.FieldReferenceFromString(pass.Field)
+	if err != nil {
+		return nil, err
+	}
+
+	return &compiler.AddEnumValue{
+		ObjectRef: compiler.ObjectReference{},
+		FieldRef:  fieldRef,
+		Name:      pass.Name,
+		Value:     pass.Value,
+	}, nil
+}