diff --git a/Android.bp b/Android.bp
index 84ac82f..7465341 100644
--- a/Android.bp
+++ b/Android.bp
@@ -55,6 +55,7 @@
         "android/namespace.go",
         "android/neverallow.go",
         "android/onceper.go",
+        "android/override_module.go",
         "android/package_ctx.go",
         "android/path_properties.go",
         "android/paths.go",
diff --git a/android/mutator.go b/android/mutator.go
index 6c9f17a..71237a1 100644
--- a/android/mutator.go
+++ b/android/mutator.go
@@ -79,6 +79,7 @@
 	RegisterNamespaceMutator,
 	RegisterPrebuiltsPreArchMutators,
 	RegisterDefaultsPreArchMutators,
+	RegisterOverridePreArchMutators,
 }
 
 func registerArchMutator(ctx RegisterMutatorsContext) {
diff --git a/android/override_module.go b/android/override_module.go
new file mode 100644
index 0000000..02db359
--- /dev/null
+++ b/android/override_module.go
@@ -0,0 +1,213 @@
+// Copyright (C) 2019 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package android
+
+// This file contains all the foundation components for override modules and their base module
+// types. Override modules are a kind of opposite of default modules in that they override certain
+// properties of an existing base module whereas default modules provide base module data to be
+// overridden. However, unlike default and defaultable module pairs, both override and overridable
+// modules generate and output build actions, and it is up to product make vars to decide which one
+// to actually build and install in the end. In other words, default modules and defaultable modules
+// can be compared to abstract classes and concrete classes in C++ and Java. By the same analogy,
+// both override and overridable modules act like concrete classes.
+//
+// There is one more crucial difference from the logic perspective. Unlike default pairs, most Soong
+// actions happen in the base (overridable) module by creating a local variant for each override
+// module based on it.
+
+import (
+	"sync"
+
+	"github.com/google/blueprint"
+	"github.com/google/blueprint/proptools"
+)
+
+// Interface for override module types, e.g. override_android_app, override_apex
+type OverrideModule interface {
+	Module
+
+	getOverridingProperties() []interface{}
+	setOverridingProperties(properties []interface{})
+
+	getOverrideModuleProperties() *OverrideModuleProperties
+}
+
+// Base module struct for override module types
+type OverrideModuleBase struct {
+	moduleProperties OverrideModuleProperties
+
+	overridingProperties []interface{}
+}
+
+type OverrideModuleProperties struct {
+	// Name of the base module to be overridden
+	Base *string
+
+	// TODO(jungjw): Add an optional override_name bool flag.
+}
+
+func (o *OverrideModuleBase) getOverridingProperties() []interface{} {
+	return o.overridingProperties
+}
+
+func (o *OverrideModuleBase) setOverridingProperties(properties []interface{}) {
+	o.overridingProperties = properties
+}
+
+func (o *OverrideModuleBase) getOverrideModuleProperties() *OverrideModuleProperties {
+	return &o.moduleProperties
+}
+
+func InitOverrideModule(m OverrideModule) {
+	m.setOverridingProperties(m.GetProperties())
+
+	m.AddProperties(m.getOverrideModuleProperties())
+}
+
+// Interface for overridable module types, e.g. android_app, apex
+type OverridableModule interface {
+	setOverridableProperties(prop []interface{})
+
+	addOverride(o OverrideModule)
+	getOverrides() []OverrideModule
+
+	override(ctx BaseModuleContext, o OverrideModule)
+
+	setOverridesProperty(overridesProperties *[]string)
+}
+
+// Base module struct for overridable module types
+type OverridableModuleBase struct {
+	ModuleBase
+
+	// List of OverrideModules that override this base module
+	overrides []OverrideModule
+	// Used to parallelize registerOverrideMutator executions. Note that only addOverride locks this
+	// mutex. It is because addOverride and getOverride are used in different mutators, and so are
+	// guaranteed to be not mixed. (And, getOverride only reads from overrides, and so don't require
+	// mutex locking.)
+	overridesLock sync.Mutex
+
+	overridableProperties []interface{}
+
+	// If an overridable module has a property to list other modules that itself overrides, it should
+	// set this to a pointer to the property through the InitOverridableModule function, so that
+	// override information is propagated and aggregated correctly.
+	overridesProperty *[]string
+}
+
+func InitOverridableModule(m OverridableModule, overridesProperty *[]string) {
+	m.setOverridableProperties(m.(Module).GetProperties())
+	m.setOverridesProperty(overridesProperty)
+}
+
+func (b *OverridableModuleBase) setOverridableProperties(prop []interface{}) {
+	b.overridableProperties = prop
+}
+
+func (b *OverridableModuleBase) addOverride(o OverrideModule) {
+	b.overridesLock.Lock()
+	b.overrides = append(b.overrides, o)
+	b.overridesLock.Unlock()
+}
+
+// Should NOT be used in the same mutator as addOverride.
+func (b *OverridableModuleBase) getOverrides() []OverrideModule {
+	return b.overrides
+}
+
+func (b *OverridableModuleBase) setOverridesProperty(overridesProperty *[]string) {
+	b.overridesProperty = overridesProperty
+}
+
+// Overrides a base module with the given OverrideModule.
+func (b *OverridableModuleBase) override(ctx BaseModuleContext, o OverrideModule) {
+	for _, p := range b.overridableProperties {
+		for _, op := range o.getOverridingProperties() {
+			if proptools.TypeEqual(p, op) {
+				err := proptools.PrependProperties(p, op, nil)
+				if err != nil {
+					if propertyErr, ok := err.(*proptools.ExtendPropertyError); ok {
+						ctx.PropertyErrorf(propertyErr.Property, "%s", propertyErr.Err.Error())
+					} else {
+						panic(err)
+					}
+				}
+			}
+		}
+	}
+	// Adds the base module to the overrides property, if exists, of the overriding module. See the
+	// comment on OverridableModuleBase.overridesProperty for details.
+	if b.overridesProperty != nil {
+		*b.overridesProperty = append(*b.overridesProperty, b.Name())
+	}
+	// The base module name property has to be updated separately for Name() to work as intended.
+	b.module.base().nameProperties.Name = proptools.StringPtr(o.Name())
+}
+
+// Mutators for override/overridable modules. All the fun happens in these functions. It is critical
+// to keep them in this order and not put any order mutators between them.
+func RegisterOverridePreArchMutators(ctx RegisterMutatorsContext) {
+	ctx.BottomUp("override_deps", overrideModuleDepsMutator).Parallel()
+	ctx.TopDown("register_override", registerOverrideMutator).Parallel()
+	ctx.BottomUp("perform_override", performOverrideMutator).Parallel()
+}
+
+type overrideBaseDependencyTag struct {
+	blueprint.BaseDependencyTag
+}
+
+var overrideBaseDepTag overrideBaseDependencyTag
+
+// Adds dependency on the base module to the overriding module so that they can be visited in the
+// next phase.
+func overrideModuleDepsMutator(ctx BottomUpMutatorContext) {
+	if module, ok := ctx.Module().(OverrideModule); ok {
+		ctx.AddDependency(ctx.Module(), overrideBaseDepTag, *module.getOverrideModuleProperties().Base)
+	}
+}
+
+// Visits the base module added as a dependency above, checks the module type, and registers the
+// overriding module.
+func registerOverrideMutator(ctx TopDownMutatorContext) {
+	ctx.VisitDirectDepsWithTag(overrideBaseDepTag, func(base Module) {
+		if o, ok := base.(OverridableModule); ok {
+			o.addOverride(ctx.Module().(OverrideModule))
+		} else {
+			ctx.PropertyErrorf("base", "unsupported base module type")
+		}
+	})
+}
+
+// Now, goes through all overridable modules, finds all modules overriding them, creates a local
+// variant for each of them, and performs the actual overriding operation by calling override().
+func performOverrideMutator(ctx BottomUpMutatorContext) {
+	if b, ok := ctx.Module().(OverridableModule); ok {
+		overrides := b.getOverrides()
+		if len(overrides) == 0 {
+			return
+		}
+		variants := make([]string, len(overrides)+1)
+		// The first variant is for the original, non-overridden, base module.
+		variants[0] = ""
+		for i, o := range overrides {
+			variants[i+1] = o.(Module).Name()
+		}
+		mods := ctx.CreateLocalVariations(variants...)
+		for i, o := range overrides {
+			mods[i+1].(OverridableModule).override(ctx, o)
+		}
+	}
+}
diff --git a/java/app.go b/java/app.go
index 8f5d010..b31f232 100644
--- a/java/app.go
+++ b/java/app.go
@@ -33,16 +33,13 @@
 	android.RegisterModuleType("android_test", AndroidTestFactory)
 	android.RegisterModuleType("android_test_helper_app", AndroidTestHelperAppFactory)
 	android.RegisterModuleType("android_app_certificate", AndroidAppCertificateFactory)
+	android.RegisterModuleType("override_android_app", OverrideAndroidAppModuleFactory)
 }
 
 // AndroidManifest.xml merging
 // package splits
 
 type appProperties struct {
-	// The name of a certificate in the default certificate directory, blank to use the default product certificate,
-	// or an android_app_certificate module name in the form ":module".
-	Certificate *string
-
 	// Names of extra android_app_certificate modules to sign the apk with in the form ":module".
 	Additional_certificates []string
 
@@ -79,14 +76,24 @@
 	Use_embedded_dex *bool
 }
 
+// android_app properties that can be overridden by override_android_app
+type overridableAppProperties struct {
+	// The name of a certificate in the default certificate directory, blank to use the default product certificate,
+	// or an android_app_certificate module name in the form ":module".
+	Certificate *string
+}
+
 type AndroidApp struct {
 	Library
 	aapt
+	android.OverridableModuleBase
 
 	certificate Certificate
 
 	appProperties appProperties
 
+	overridableAppProperties overridableAppProperties
+
 	installJniLibs []jniLib
 
 	bundleFile android.Path
@@ -320,7 +327,7 @@
 
 func (a *AndroidApp) generateAndroidBuildActions(ctx android.ModuleContext) {
 	// Check if the install APK name needs to be overridden.
-	a.installApkName = ctx.DeviceConfig().OverridePackageNameFor(ctx.ModuleName())
+	a.installApkName = ctx.DeviceConfig().OverridePackageNameFor(a.Name())
 
 	// Process all building blocks, from AAPT to certificates.
 	a.aaptBuildActions(ctx)
@@ -339,6 +346,7 @@
 	certificates := a.certificateBuildActions(certificateDeps, ctx)
 
 	// Build a final signed app package.
+	// TODO(jungjw): Consider changing this to installApkName.
 	packageFile := android.PathForModuleOut(ctx, ctx.ModuleName()+".apk")
 	CreateAppPackage(ctx, packageFile, a.exportPackage, jniJarFile, dexJarFile, certificates)
 	a.outputFile = packageFile
@@ -413,7 +421,7 @@
 	if overridden {
 		return ":" + certificate
 	}
-	return String(a.appProperties.Certificate)
+	return String(a.overridableAppProperties.Certificate)
 }
 
 // android_app compiles sources and Android resources into an Android application package `.apk` file.
@@ -432,7 +440,8 @@
 		&module.Module.dexpreoptProperties,
 		&module.Module.protoProperties,
 		&module.aaptProperties,
-		&module.appProperties)
+		&module.appProperties,
+		&module.overridableAppProperties)
 
 	module.Prefer32(func(ctx android.BaseModuleContext, base *android.ModuleBase, class android.OsClass) bool {
 		return class == android.Device && ctx.Config().DevicePrefer32BitApps()
@@ -440,6 +449,7 @@
 
 	android.InitAndroidMultiTargetsArchModule(module, android.DeviceSupported, android.MultilibCommon)
 	android.InitDefaultableModule(module)
+	android.InitOverridableModule(module, &module.appProperties.Overrides)
 
 	return module
 }
@@ -503,6 +513,7 @@
 		&module.aaptProperties,
 		&module.appProperties,
 		&module.appTestProperties,
+		&module.overridableAppProperties,
 		&module.testProperties)
 
 	android.InitAndroidMultiTargetsArchModule(module, android.DeviceSupported, android.MultilibCommon)
@@ -541,7 +552,8 @@
 		&module.Module.protoProperties,
 		&module.aaptProperties,
 		&module.appProperties,
-		&module.appTestHelperAppProperties)
+		&module.appTestHelperAppProperties,
+		&module.overridableAppProperties)
 
 	android.InitAndroidMultiTargetsArchModule(module, android.DeviceSupported, android.MultilibCommon)
 	android.InitDefaultableModule(module)
@@ -575,3 +587,24 @@
 		android.PathForModuleSrc(ctx, cert+".pk8"),
 	}
 }
+
+type OverrideAndroidApp struct {
+	android.ModuleBase
+	android.OverrideModuleBase
+}
+
+func (i *OverrideAndroidApp) GenerateAndroidBuildActions(ctx android.ModuleContext) {
+	// All the overrides happen in the base module.
+	// TODO(jungjw): Check the base module type.
+}
+
+// override_android_app is used to create an android_app module based on another android_app by overriding
+// some of its properties.
+func OverrideAndroidAppModuleFactory() android.Module {
+	m := &OverrideAndroidApp{}
+	m.AddProperties(&overridableAppProperties{})
+
+	android.InitAndroidModule(m)
+	android.InitOverrideModule(m)
+	return m
+}
diff --git a/java/app_test.go b/java/app_test.go
index 1bad123..cf57c80 100644
--- a/java/app_test.go
+++ b/java/app_test.go
@@ -827,3 +827,75 @@
 		t.Errorf("target package renaming flag, %q is missing in aapt2 link flags, %q", e, aapt2Flags)
 	}
 }
+
+func TestOverrideAndroidApp(t *testing.T) {
+	ctx := testJava(t, `
+		android_app {
+			name: "foo",
+			srcs: ["a.java"],
+			overrides: ["baz"],
+		}
+
+		override_android_app {
+			name: "bar",
+			base: "foo",
+			certificate: ":new_certificate",
+		}
+
+		android_app_certificate {
+			name: "new_certificate",
+			certificate: "cert/new_cert",
+		}
+		`)
+
+	expectedVariants := []struct {
+		variantName string
+		apkName     string
+		apkPath     string
+		signFlag    string
+		overrides   []string
+	}{
+		{
+			variantName: "android_common",
+			apkPath:     "/target/product/test_device/system/app/foo/foo.apk",
+			signFlag:    "build/target/product/security/testkey.x509.pem build/target/product/security/testkey.pk8",
+			overrides:   []string{"baz"},
+		},
+		{
+			variantName: "bar_android_common",
+			apkPath:     "/target/product/test_device/system/app/bar/bar.apk",
+			signFlag:    "cert/new_cert.x509.pem cert/new_cert.pk8",
+			overrides:   []string{"baz", "foo"},
+		},
+	}
+	for _, expected := range expectedVariants {
+		variant := ctx.ModuleForTests("foo", expected.variantName)
+
+		// Check the final apk name
+		outputs := variant.AllOutputs()
+		expectedApkPath := buildDir + expected.apkPath
+		found := false
+		for _, o := range outputs {
+			if o == expectedApkPath {
+				found = true
+				break
+			}
+		}
+		if !found {
+			t.Errorf("Can't find %q in output files.\nAll outputs:%v", expectedApkPath, outputs)
+		}
+
+		// Check the certificate paths
+		signapk := variant.Output("foo.apk")
+		signFlag := signapk.Args["certificates"]
+		if expected.signFlag != signFlag {
+			t.Errorf("Incorrect signing flags, expected: %q, got: %q", expected.signFlag, signFlag)
+		}
+
+		mod := variant.Module().(*AndroidApp)
+		if !reflect.DeepEqual(expected.overrides, mod.appProperties.Overrides) {
+			t.Errorf("Incorrect overrides property value, expected: %q, got: %q",
+				expected.overrides, mod.appProperties.Overrides)
+		}
+	}
+}
diff --git a/java/java.go b/java/java.go
index e0da006..3eae932 100644
--- a/java/java.go
+++ b/java/java.go
@@ -2068,6 +2068,7 @@
 		&androidLibraryProperties{},
 		&appProperties{},
 		&appTestProperties{},
+		&overridableAppProperties{},
 		&ImportProperties{},
 		&AARImportProperties{},
 		&sdkLibraryProperties{},
diff --git a/java/java_test.go b/java/java_test.go
index 35dd696..ec6d27a 100644
--- a/java/java_test.go
+++ b/java/java_test.go
@@ -86,10 +86,12 @@
 	ctx.RegisterModuleType("droiddoc_host", android.ModuleFactoryAdaptor(DroiddocHostFactory))
 	ctx.RegisterModuleType("droiddoc_template", android.ModuleFactoryAdaptor(ExportedDroiddocDirFactory))
 	ctx.RegisterModuleType("java_sdk_library", android.ModuleFactoryAdaptor(SdkLibraryFactory))
+	ctx.RegisterModuleType("override_android_app", android.ModuleFactoryAdaptor(OverrideAndroidAppModuleFactory))
 	ctx.RegisterModuleType("prebuilt_apis", android.ModuleFactoryAdaptor(PrebuiltApisFactory))
 	ctx.PreArchMutators(android.RegisterPrebuiltsPreArchMutators)
 	ctx.PreArchMutators(android.RegisterPrebuiltsPostDepsMutators)
 	ctx.PreArchMutators(android.RegisterDefaultsPreArchMutators)
+	ctx.PreArchMutators(android.RegisterOverridePreArchMutators)
 	ctx.PreArchMutators(func(ctx android.RegisterMutatorsContext) {
 		ctx.TopDown("prebuilt_apis", PrebuiltApisMutator).Parallel()
 		ctx.TopDown("java_sdk_library", SdkLibraryMutator).Parallel()