diff --git a/Libraries/ActionSheetIOS/RCTActionSheetManager.m b/Libraries/ActionSheetIOS/RCTActionSheetManager.m
index 34a791520..dbaa9affd 100644
--- a/Libraries/ActionSheetIOS/RCTActionSheetManager.m
+++ b/Libraries/ActionSheetIOS/RCTActionSheetManager.m
@@ -43,6 +43,11 @@ RCT_EXPORT_METHOD(showActionSheetWithOptions:(NSDictionary *)options
                   failureCallback:(__unused RCTResponseSenderBlock)failureCallback
                   successCallback:(RCTResponseSenderBlock)successCallback)
 {
+  if (RCTRunningInAppExtension()) {
+    RCTLogError(@"Unable to show action sheet from app extension");
+    return;
+  }
+  
   UIActionSheet *actionSheet = [UIActionSheet new];
 
   actionSheet.title = options[@"title"];
@@ -62,7 +67,7 @@ RCT_EXPORT_METHOD(showActionSheetWithOptions:(NSDictionary *)options
 
   _callbacks[RCTKeyForInstance(actionSheet)] = successCallback;
 
-  UIWindow *appWindow = [UIApplication sharedApplication].delegate.window;
+  UIWindow *appWindow = RCTSharedApplication().delegate.window;
   if (appWindow == nil) {
     RCTLogError(@"Tried to display action sheet but there is no application window. options: %@", options);
     return;
@@ -87,8 +92,13 @@ RCT_EXPORT_METHOD(showShareActionSheetWithOptions:(NSDictionary *)options
     failureCallback(@[@"No `url` or `message` to share"]);
     return;
   }
+  if (RCTRunningInAppExtension()) {
+    failureCallback(@[@"Unable to show action sheet from app extension"]);
+    return;
+  }
+
   UIActivityViewController *share = [[UIActivityViewController alloc] initWithActivityItems:items applicationActivities:nil];
-  UIViewController *ctrl = [UIApplication sharedApplication].delegate.window.rootViewController;
+  UIViewController *ctrl = RCTSharedApplication().delegate.window.rootViewController;
 
 #if __IPHONE_OS_VERSION_MIN_REQUIRED < __IPHONE_8_0
 
@@ -146,7 +156,7 @@ RCT_EXPORT_METHOD(showShareActionSheetWithOptions:(NSDictionary *)options
     RCTLogWarn(@"No callback registered for action sheet: %@", actionSheet.title);
   }
 
-  [[UIApplication sharedApplication].delegate.window makeKeyWindow];
+  [RCTSharedApplication().delegate.window makeKeyWindow];
 }
 
 #pragma mark Private
diff --git a/Libraries/CameraRoll/RCTImagePickerManager.m b/Libraries/CameraRoll/RCTImagePickerManager.m
index 00a28a665..281149196 100644
--- a/Libraries/CameraRoll/RCTImagePickerManager.m
+++ b/Libraries/CameraRoll/RCTImagePickerManager.m
@@ -10,6 +10,8 @@
 
 #import "RCTImagePickerManager.h"
 #import "RCTRootView.h"
+#import "RCTLog.h"
+#import "RCTUtils.h"
 
 #import <UIKit/UIKit.h>
 
@@ -53,7 +55,12 @@ RCT_EXPORT_METHOD(openCameraDialog:(NSDictionary *)config
                   successCallback:(RCTResponseSenderBlock)callback
                   cancelCallback:(RCTResponseSenderBlock)cancelCallback)
 {
-  UIWindow *keyWindow = [UIApplication sharedApplication].keyWindow;
+  if (RCTRunningInAppExtension()) {
+    cancelCallback(@[@"Camera access is unavailable in an app extension"]);
+    return;
+  }
+  
+  UIWindow *keyWindow = RCTSharedApplication().keyWindow;
   UIViewController *rootViewController = keyWindow.rootViewController;
 
   UIImagePickerController *imagePicker = [UIImagePickerController new];
@@ -75,7 +82,12 @@ RCT_EXPORT_METHOD(openSelectDialog:(NSDictionary *)config
                   successCallback:(RCTResponseSenderBlock)callback
                   cancelCallback:(RCTResponseSenderBlock)cancelCallback)
 {
-  UIWindow *keyWindow = [UIApplication sharedApplication].keyWindow;
+  if (RCTRunningInAppExtension()) {
+    cancelCallback(@[@"Image picker is currently unavailable in an app extension"]);
+    return;
+  }
+  
+  UIWindow *keyWindow = RCTSharedApplication().keyWindow;
   UIViewController *rootViewController = keyWindow.rootViewController;
 
   UIImagePickerController *imagePicker = [UIImagePickerController new];
@@ -109,7 +121,7 @@ didFinishPickingMediaWithInfo:(NSDictionary *)info
   [_pickerCallbacks removeObjectAtIndex:index];
   [_pickerCancelCallbacks removeObjectAtIndex:index];
 
-  UIWindow *keyWindow = [UIApplication sharedApplication].keyWindow;
+  UIWindow *keyWindow = RCTSharedApplication().keyWindow;
   UIViewController *rootViewController = keyWindow.rootViewController;
   [rootViewController dismissViewControllerAnimated:YES completion:nil];
 
@@ -125,7 +137,7 @@ didFinishPickingMediaWithInfo:(NSDictionary *)info
   [_pickerCallbacks removeObjectAtIndex:index];
   [_pickerCancelCallbacks removeObjectAtIndex:index];
 
-  UIWindow *keyWindow = [UIApplication sharedApplication].keyWindow;
+  UIWindow *keyWindow = RCTSharedApplication().keyWindow;
   UIViewController *rootViewController = keyWindow.rootViewController;
   [rootViewController dismissViewControllerAnimated:YES completion:nil];
 
diff --git a/Libraries/LinkingIOS/RCTLinkingManager.m b/Libraries/LinkingIOS/RCTLinkingManager.m
index af1d41752..37a2cc4d6 100644
--- a/Libraries/LinkingIOS/RCTLinkingManager.m
+++ b/Libraries/LinkingIOS/RCTLinkingManager.m
@@ -58,14 +58,20 @@ RCT_EXPORT_MODULE()
 RCT_EXPORT_METHOD(openURL:(NSURL *)URL)
 {
   // Doesn't really matter what thread we call this on since it exits the app
-  [[UIApplication sharedApplication] openURL:URL];
+  [RCTSharedApplication() openURL:URL];
 }
 
 RCT_EXPORT_METHOD(canOpenURL:(NSURL *)URL
                   callback:(RCTResponseSenderBlock)callback)
 {
+  if (RCTRunningInAppExtension()) {
+    // Technically Today widgets can open urls, but supporting that would require
+    // a reference to the NSExtensionContext
+    callback(@[@(NO)]);
+  }
+
   // This can be expensive, so we deliberately don't call on main thread
-  BOOL canOpen = [[UIApplication sharedApplication] canOpenURL:URL];
+  BOOL canOpen = [RCTSharedApplication() canOpenURL:URL];
   callback(@[@(canOpen)]);
 }
 
diff --git a/Libraries/PushNotificationIOS/RCTPushNotificationManager.m b/Libraries/PushNotificationIOS/RCTPushNotificationManager.m
index fda9980f9..6af5f8e91 100644
--- a/Libraries/PushNotificationIOS/RCTPushNotificationManager.m
+++ b/Libraries/PushNotificationIOS/RCTPushNotificationManager.m
@@ -122,7 +122,7 @@ RCT_EXPORT_MODULE()
  */
 RCT_EXPORT_METHOD(setApplicationIconBadgeNumber:(NSInteger)number)
 {
-  [UIApplication sharedApplication].applicationIconBadgeNumber = number;
+  RCTSharedApplication().applicationIconBadgeNumber = number;
 }
 
 /**
@@ -131,12 +131,16 @@ RCT_EXPORT_METHOD(setApplicationIconBadgeNumber:(NSInteger)number)
 RCT_EXPORT_METHOD(getApplicationIconBadgeNumber:(RCTResponseSenderBlock)callback)
 {
   callback(@[
-    @([UIApplication sharedApplication].applicationIconBadgeNumber)
+    @(RCTSharedApplication().applicationIconBadgeNumber)
   ]);
 }
 
 RCT_EXPORT_METHOD(requestPermissions:(NSDictionary *)permissions)
 {
+  if (RCTRunningInAppExtension()) {
+    return;
+  }
+
   UIUserNotificationType types = UIUserNotificationTypeNone;
   if (permissions) {
     if ([permissions[@"alert"] boolValue]) {
@@ -152,35 +156,37 @@ RCT_EXPORT_METHOD(requestPermissions:(NSDictionary *)permissions)
     types = UIUserNotificationTypeAlert | UIUserNotificationTypeBadge | UIUserNotificationTypeSound;
   }
 
+  UIApplication *app = RCTSharedApplication();
 #if __IPHONE_OS_VERSION_MIN_REQUIRED >= __IPHONE_8_0
-
   id notificationSettings = [UIUserNotificationSettings settingsForTypes:types categories:nil];
-  [[UIApplication sharedApplication] registerUserNotificationSettings:notificationSettings];
-  [[UIApplication sharedApplication] registerForRemoteNotifications];
-
+  [app registerUserNotificationSettings:notificationSettings];
+  [app registerForRemoteNotifications];
 #else
-
-  [[UIApplication sharedApplication] registerForRemoteNotificationTypes:types];
-
+  [app registerForRemoteNotificationTypes:types];
 #endif
-
 }
 
 RCT_EXPORT_METHOD(abandonPermissions)
 {
-  [[UIApplication sharedApplication] unregisterForRemoteNotifications];
+  [RCTSharedApplication() unregisterForRemoteNotifications];
 }
 
 RCT_EXPORT_METHOD(checkPermissions:(RCTResponseSenderBlock)callback)
 {
+  if (RCTRunningInAppExtension()) {
+    NSDictionary *permissions = @{@"alert": @(NO), @"badge": @(NO), @"sound": @(NO)};
+    callback(@[permissions]);
+    return;
+  }
+
   NSUInteger types = 0;
   if ([UIApplication instancesRespondToSelector:@selector(currentUserNotificationSettings)]) {
-    types = [[UIApplication sharedApplication] currentUserNotificationSettings].types;
+    types = [RCTSharedApplication() currentUserNotificationSettings].types;
   } else {
 
 #if __IPHONE_OS_VERSION_MIN_REQUIRED < __IPHONE_8_0
 
-    types = [[UIApplication sharedApplication] enabledRemoteNotificationTypes];
+    types = [RCTSharedApplication() enabledRemoteNotificationTypes];
 
 #endif
 
@@ -203,13 +209,13 @@ RCT_EXPORT_METHOD(checkPermissions:(RCTResponseSenderBlock)callback)
 
 RCT_EXPORT_METHOD(presentLocalNotification:(UILocalNotification *)notification)
 {
-  [[UIApplication sharedApplication] presentLocalNotificationNow:notification];
+  [RCTSharedApplication() presentLocalNotificationNow:notification];
 }
 
 
 RCT_EXPORT_METHOD(scheduleLocalNotification:(UILocalNotification *)notification)
 {
-  [[UIApplication sharedApplication] scheduleLocalNotification:notification];
+  [RCTSharedApplication() scheduleLocalNotification:notification];
 }
 
 @end
diff --git a/React/Base/RCTPerfStats.m b/React/Base/RCTPerfStats.m
index ba841dc67..462aa0f9e 100644
--- a/React/Base/RCTPerfStats.m
+++ b/React/Base/RCTPerfStats.m
@@ -10,6 +10,7 @@
 #import "RCTPerfStats.h"
 
 #import "RCTDefines.h"
+#import "RCTUtils.h"
 
 #if RCT_DEV
 
@@ -66,7 +67,11 @@ RCT_EXPORT_MODULE()
 
 - (void)show
 {
-  UIView *targetView = [UIApplication sharedApplication].delegate.window.rootViewController.view;
+  if (RCTRunningInAppExtension()) {
+    return;
+  }
+  
+  UIView *targetView = RCTSharedApplication().delegate.window.rootViewController.view;
 
   targetView.frame = (CGRect){
     targetView.frame.origin,
diff --git a/React/Base/RCTUtils.h b/React/Base/RCTUtils.h
index 65eb99f8c..bc94d62f8 100644
--- a/React/Base/RCTUtils.h
+++ b/React/Base/RCTUtils.h
@@ -11,6 +11,7 @@
 
 #import <CoreGraphics/CoreGraphics.h>
 #import <Foundation/Foundation.h>
+#import <UIKit/UIKit.h>
 
 #import "RCTAssert.h"
 #import "RCTDefines.h"
@@ -51,6 +52,16 @@ RCT_EXTERN NSDictionary *RCTJSErrorFromNSError(NSError *error);
 // Returns YES if React is running in a test environment
 RCT_EXTERN BOOL RCTRunningInTestEnvironment(void);
 
+// Returns YES if React is running in an iOS App Extension
+RCT_EXTERN BOOL RCTRunningInAppExtension(void);
+
+// Returns the shared UIApplication instance, or nil if running in an App Extension
+RCT_EXTERN UIApplication *RCTSharedApplication(void);
+
+// Return a UIAlertView initialized with the given values
+// or nil if running in an app extension
+RCT_EXTERN UIAlertView *RCTAlertView(NSString *title, NSString *message, id delegate, NSString *cancelButtonTitle, NSArray *otherButtonTitles);
+
 // Return YES if image has an alpha component
 RCT_EXTERN BOOL RCTImageHasAlpha(CGImageRef image);
 
diff --git a/React/Base/RCTUtils.m b/React/Base/RCTUtils.m
index 2fba55f00..c3e59b06f 100644
--- a/React/Base/RCTUtils.m
+++ b/React/Base/RCTUtils.m
@@ -337,6 +337,42 @@ BOOL RCTRunningInTestEnvironment(void)
   return isTestEnvironment;
 }
 
+BOOL RCTRunningInAppExtension(void)
+{
+  return [[[[NSBundle mainBundle] bundlePath] pathExtension] isEqualToString:@"appex"];
+}
+
+id RCTSharedApplication(void)
+{
+  if (RCTRunningInAppExtension()) {
+    return nil;
+  }
+  
+  return [[UIApplication class] performSelector:@selector(sharedApplication)];
+}
+
+id RCTAlertView(NSString *title, NSString *message, id delegate, NSString *cancelButtonTitle, NSArray *otherButtonTitles)
+{
+  if (RCTRunningInAppExtension()) {
+    RCTLogError(@"RCTAlertView is unavailable when running in an app extension");
+    return nil;
+  }
+  
+  UIAlertView *alertView = [[UIAlertView alloc] init];
+  alertView.title = title;
+  alertView.message = message;
+  alertView.delegate = delegate;
+  if (cancelButtonTitle != nil) {
+    [alertView addButtonWithTitle:cancelButtonTitle];
+    alertView.cancelButtonIndex = 0;
+  }
+  for (NSString *buttonTitle in otherButtonTitles)
+  {
+    [alertView addButtonWithTitle:buttonTitle];
+  }
+  return alertView;
+}
+
 BOOL RCTImageHasAlpha(CGImageRef image)
 {
   switch (CGImageGetAlphaInfo(image)) {
diff --git a/React/Modules/RCTAlertManager.m b/React/Modules/RCTAlertManager.m
index b0475e231..b07dcde54 100644
--- a/React/Modules/RCTAlertManager.m
+++ b/React/Modules/RCTAlertManager.m
@@ -11,6 +11,7 @@
 
 #import "RCTAssert.h"
 #import "RCTLog.h"
+#import "RCTUtils.h"
 
 @interface RCTAlertManager() <UIAlertViewDelegate>
 
@@ -76,13 +77,12 @@ RCT_EXPORT_METHOD(alertWithArgs:(NSDictionary *)args
     RCTLogError(@"Must have at least one button.");
     return;
   }
-
-  UIAlertView *alertView = [[UIAlertView alloc] initWithTitle:title
-                                                      message:nil
-                                                     delegate:self
-                                            cancelButtonTitle:nil
-                                            otherButtonTitles:nil];
-
+  
+  if (RCTRunningInAppExtension()) {
+    return;
+  }
+  
+  UIAlertView *alertView = RCTAlertView(title, nil, self, nil, nil);
   NSMutableArray *buttonKeys = [[NSMutableArray alloc] initWithCapacity:buttons.count];
 
   if ([type isEqualToString:@"plain-text"]) {
diff --git a/React/Modules/RCTAppState.m b/React/Modules/RCTAppState.m
index a72ea2cc3..294330643 100644
--- a/React/Modules/RCTAppState.m
+++ b/React/Modules/RCTAppState.m
@@ -12,6 +12,7 @@
 #import "RCTAssert.h"
 #import "RCTBridge.h"
 #import "RCTEventDispatcher.h"
+#import "RCTUtils.h"
 
 static NSString *RCTCurrentAppBackgroundState()
 {
@@ -25,7 +26,11 @@ static NSString *RCTCurrentAppBackgroundState()
     };
   });
 
-  return states[@([UIApplication sharedApplication].applicationState)] ?: @"unknown";
+  if (RCTRunningInAppExtension()) {
+    return @"extension";
+  }
+
+  return states[@(RCTSharedApplication().applicationState)] ?: @"unknown";
 }
 
 @implementation RCTAppState
diff --git a/React/Modules/RCTDevMenu.m b/React/Modules/RCTDevMenu.m
index 63ac438d1..98335d7b4 100644
--- a/React/Modules/RCTDevMenu.m
+++ b/React/Modules/RCTDevMenu.m
@@ -407,11 +407,8 @@ RCT_EXPORT_MODULE()
   Class chromeExecutorClass = NSClassFromString(@"RCTWebSocketExecutor");
   if (!chromeExecutorClass) {
     [items addObject:[RCTDevMenuItem buttonItemWithTitle:@"Chrome Debugger Unavailable" handler:^{
-      [[[UIAlertView alloc] initWithTitle:@"Chrome Debugger Unavailable"
-                                  message:@"You need to include the RCTWebSocket library to enable Chrome debugging"
-                                 delegate:nil
-                        cancelButtonTitle:@"OK"
-                        otherButtonTitles:nil] show];
+      UIAlertView *alert = RCTAlertView(@"Chrome Debugger Unavailable", @"You need to include the RCTWebSocket library to enable Chrome debugging", nil, @"OK", nil);
+      [alert show];
     }]];
   } else {
     BOOL isDebuggingInChrome = _executorClass && _executorClass == chromeExecutorClass;
@@ -447,7 +444,7 @@ RCT_EXPORT_MODULE()
 
 RCT_EXPORT_METHOD(show)
 {
-  if (_actionSheet || !_bridge) {
+  if (_actionSheet || !_bridge || RCTRunningInAppExtension()) {
     return;
   }
 
@@ -474,7 +471,7 @@ RCT_EXPORT_METHOD(show)
   actionSheet.cancelButtonIndex = actionSheet.numberOfButtons - 1;
 
   actionSheet.actionSheetStyle = UIBarStyleBlack;
-  [actionSheet showInView:[UIApplication sharedApplication].keyWindow.rootViewController.view];
+  [actionSheet showInView:RCTSharedApplication().keyWindow.rootViewController.view];
   _actionSheet = actionSheet;
   _presentedItems = items;
 }
diff --git a/React/Modules/RCTRedBox.m b/React/Modules/RCTRedBox.m
index 4d82278c9..ecf3fd921 100644
--- a/React/Modules/RCTRedBox.m
+++ b/React/Modules/RCTRedBox.m
@@ -126,7 +126,7 @@ RCT_NOT_IMPLEMENTED(- (instancetype)initWithCoder:(NSCoder *)aDecoder)
 {
   self.hidden = YES;
   [self resignFirstResponder];
-  [[UIApplication sharedApplication].delegate.window makeKeyWindow];
+  [RCTSharedApplication().delegate.window makeKeyWindow];
 }
 
 - (void)reload
diff --git a/React/Modules/RCTStatusBarManager.m b/React/Modules/RCTStatusBarManager.m
index ce2364e2b..893c3e0f3 100644
--- a/React/Modules/RCTStatusBarManager.m
+++ b/React/Modules/RCTStatusBarManager.m
@@ -11,6 +11,7 @@
 
 #import "RCTEventDispatcher.h"
 #import "RCTLog.h"
+#import "RCTUtils.h"
 
 @implementation RCTConvert (UIStatusBar)
 
@@ -97,8 +98,8 @@ RCT_EXPORT_METHOD(setStyle:(UIStatusBarStyle)statusBarStyle
     RCTLogError(@"RCTStatusBarManager module requires that the \
                 UIViewControllerBasedStatusBarAppearance key in the Info.plist is set to NO");
   } else {
-    [[UIApplication sharedApplication] setStatusBarStyle:statusBarStyle
-                                                animated:animated];
+    [RCTSharedApplication() setStatusBarStyle:statusBarStyle
+                                     animated:animated];
   }
 }
 
@@ -109,14 +110,14 @@ RCT_EXPORT_METHOD(setHidden:(BOOL)hidden
     RCTLogError(@"RCTStatusBarManager module requires that the \
                 UIViewControllerBasedStatusBarAppearance key in the Info.plist is set to NO");
   } else {
-    [[UIApplication sharedApplication] setStatusBarHidden:hidden
-                                            withAnimation:animation];
+    [RCTSharedApplication() setStatusBarHidden:hidden
+                                 withAnimation:animation];
   }
 }
 
 RCT_EXPORT_METHOD(setNetworkActivityIndicatorVisible:(BOOL)visible)
 {
-  [UIApplication sharedApplication].networkActivityIndicatorVisible = visible;
+  RCTSharedApplication().networkActivityIndicatorVisible = visible;
 }
 
 @end