diff --git a/Signal/src/Profiles/OWSProfileManager.h b/Signal/src/Profiles/OWSProfileManager.h
index 558d596fa..5d3166b88 100644
--- a/Signal/src/Profiles/OWSProfileManager.h
+++ b/Signal/src/Profiles/OWSProfileManager.h
@@ -9,6 +9,8 @@ NS_ASSUME_NONNULL_BEGIN
 extern NSString *const kNSNotificationName_LocalProfileDidChange;
 extern NSString *const kNSNotificationName_OtherUsersProfileDidChange;
 
+extern const NSUInteger kOWSProfileManager_MaxAvatarDiameter;
+
 @class TSThread;
 @class OWSAES128Key;
 
diff --git a/Signal/src/Profiles/OWSProfileManager.m b/Signal/src/Profiles/OWSProfileManager.m
index d4e560fa1..6e7b2508f 100644
--- a/Signal/src/Profiles/OWSProfileManager.m
+++ b/Signal/src/Profiles/OWSProfileManager.m
@@ -94,6 +94,7 @@ NSString *const kOWSProfileManager_GroupWhitelistCollection = @"kOWSProfileManag
 /// The max bytes for a user's profile name, encoded in UTF8.
 /// Before encrypting and submitting we NULL pad the name data to this length.
 static const NSUInteger kOWSProfileManager_NameDataLength = 26;
+const NSUInteger kOWSProfileManager_MaxAvatarDiameter = 640;
 
 @interface OWSProfileManager ()
 
@@ -381,7 +382,7 @@ static const NSUInteger kOWSProfileManager_NameDataLength = 26;
 
     dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
         if (avatar) {
-            NSData *_Nullable data = UIImageJPEGRepresentation(avatar, 1.f);
+            NSData *data = [self processedImageDataForRawAvatar:avatar];
             OWSAssert(data);
             if (data) {
                 NSString *fileName = [[NSUUID UUID].UUIDString stringByAppendingPathExtension:@"jpg"];
@@ -398,6 +399,29 @@ static const NSUInteger kOWSProfileManager_NameDataLength = 26;
     });
 }
 
+- (NSData *)processedImageDataForRawAvatar:(UIImage *)image
+{
+    NSUInteger kMaxAvatarBytes = 5 * 1000 * 1000;
+
+    if (image.size.width != kOWSProfileManager_MaxAvatarDiameter
+        || image.size.height != kOWSProfileManager_MaxAvatarDiameter) {
+        // To help ensure the user is being shown the same cropping of their avatar as
+        // everyone else will see, we want to be sure that the image was resized before this point.
+        OWSFail(@"Avatar image should have been resized before trying to upload");
+        image = [image resizedImageToFillPixelSize:CGSizeMake(kOWSProfileManager_MaxAvatarDiameter,
+                                                       kOWSProfileManager_MaxAvatarDiameter)];
+    }
+
+    NSData *_Nullable data;
+    if (data.length > kMaxAvatarBytes) {
+        // Our avatar dimensions are so small that it's incredibly unlikely we wouldn't be able to fit our profile
+        // photo. e.g. generating pure noise at our resolution compresses to ~200k.
+        OWSFail(@"Suprised to find profile avatar was too large. Was it scaled properly? image: %@", image);
+    }
+
+    return data;
+}
+
 - (void)uploadAvatarToService:(NSData *)avatarData
                       success:(void (^)(NSString *avatarUrlPath))successBlock
                       failure:(void (^)())failureBlock
diff --git a/Signal/src/ViewControllers/ProfileViewController.m b/Signal/src/ViewControllers/ProfileViewController.m
index 45094027c..d0b51a7b9 100644
--- a/Signal/src/ViewControllers/ProfileViewController.m
+++ b/Signal/src/ViewControllers/ProfileViewController.m
@@ -280,9 +280,8 @@ NS_ASSUME_NONNULL_BEGIN
 {
     OWSAssert(image);
 
-    // TODO: Crop to square and possible resize.
-
-    self.avatar = image;
+    self.avatar = [image resizedImageToFillPixelSize:CGSizeMake(kOWSProfileManager_MaxAvatarDiameter,
+                                                         kOWSProfileManager_MaxAvatarDiameter)];
 }
 
 - (UIViewController *)fromViewController