--- a/mobile/android/app/build.gradle
+++ b/mobile/android/app/build.gradle
@@ -102,22 +102,18 @@ android {
         // Automation builds.  We use "official" rather than "automation" to drive these builds down
         // the list of configurations that Android Studio offers, thereby making it _not_ the
         // default.  This avoids a common issue with "omni.ja" not being packed into the default APK
         // built and deployed by Android Studio.
         official {
              dimension "audience"
         }
 
-        // The default user interface.
-        australis {
-            dimension "skin"
-        }
-
-        // A new user interface, currently under development.
+        // Since Firefox 57, the mobile user interface has followed the Photon design.
+        // Before Firefox 57, the user interface followed the Australis design.
         photon {
             dimension "skin"
         }
     }
 
     sourceSets {
         main {
             manifest.srcFile "${project.buildDir}/generated/source/preprocessed_manifest/AndroidManifest.xml"
@@ -412,36 +408,16 @@ def makeTaskExecutionListener(artifactRo
             // taskcluster/ci/android-stuff/kind.yml.  It's not possible to link
             // directly, so for now consumers will need to copy-paste the URL.
             switch (task.path) {
             case ':app:checkstyle':
                 def url = "${artifactRootUrl}/public/android/checkstyle/checkstyle.xml"
                 println "TEST-UNEXPECTED-FAIL | android-checkstyle | Checkstyle rule violations were found. See the report at: $url"
                 break
 
-            case ':app:lintOfficialAustralisDebug':
-                def url = "${artifactRootUrl}/public/android/lint/lint-results-officialAustralisDebug.html"
-                println "TEST-UNEXPECTED-FAIL | android-lint | Lint found errors in the project; aborting build. See the report at: $url"
-                break
-
-            case ':app:testOfficialAustralisDebugUnitTest':
-                def url = "${artifactRootUrl}/public/android/unittest/officialAustralisDebug/index.html"
-                println "TEST-UNEXPECTED-FAIL | android-test | There were failing tests. See the reports at: $url"
-                break
-
-            case ':app:findbugsHtmlOfficialAustralisDebug':
-                def url = "${artifactRootUrl}/public/android/findbugs/findbugs-officialAustralisDebug-output.html"
-                println "TEST-UNEXPECTED-FAIL | android-findbugs | Findbugs found issues in the project. See the report at: $url"
-                break
-
-            case ':app:findbugsXmlOfficialAustralisDebug':
-                def url = "${artifactRootUrl}/public/android/findbugs/findbugs-officialAustralisDebug-output.xml"
-                println "TEST-UNEXPECTED-FAIL | android-findbugs | Findbugs found issues in the project. See the report at: $url"
-                break
-
             case ':app:lintOfficialPhotonDebug':
                 def url = "${artifactRootUrl}/public/android/lint/lint-results-officialPhotonDebug.html"
                 println "TEST-UNEXPECTED-FAIL | android-lint | Lint found errors in the project; aborting build. See the report at: $url"
                 break
 
             case ':app:testOfficialPhotonDebugUnitTest':
                 def url = "${artifactRootUrl}/public/android/unittest/officialPhotonDebug/index.html"
                 println "TEST-UNEXPECTED-FAIL | android-test | There were failing tests. See the reports at: $url"

--- a/mobile/android/base/Makefile.in
+++ b/mobile/android/base/Makefile.in
@@ -229,21 +229,21 @@ endif # MOZ_INSTALL_TRACKING
 library_jars := $(subst $(NULL) ,:,$(strip $(library_jars)))
 
 gradle_dir := $(topobjdir)/gradle/build/mobile/android
 
 ifdef MOZ_BUILD_MOBILE_ANDROID_WITH_GRADLE
 .gradle.deps: .aapt.deps FORCE
 	@$(TOUCH) $@
 	$(topsrcdir)/mach gradle \
-		app:assembleOfficialAustralisDebug app:assembleOfficialAustralisDebugAndroidTest -x lint
+		app:assembleOfficialPhotonDebug app:assembleOfficialPhotonDebugAndroidTest -x lint
 
 classes.dex: .gradle.deps
 	$(REPORT_BUILD)
-	cp $(gradle_dir)/app/intermediates/transforms/dex/officialAustralis/debug/folders/1000/1f/main/classes.dex $@
+	cp $(gradle_dir)/app/intermediates/transforms/dex/officialPhoton/debug/folders/1000/1f/main/classes.dex $@
 else
 classes.dex: .proguard.deps
 	$(REPORT_BUILD)
 	$(DX) --dex --output=classes.dex --force-jumbo jars-proguarded
 endif
 
 ifdef MOZ_DISABLE_PROGUARD
   PROGUARD_PASSES=0
@@ -475,17 +475,17 @@ endef
 # further no-op build do work.  See also
 # toolkit/mozapps/installer/packager.mk.
 
 # .aapt.deps: $(all_resources)
 $(eval $(call aapt_command,.aapt.deps,$(all_resources),gecko.ap_,generated/,./))
 
 ifdef MOZ_BUILD_MOBILE_ANDROID_WITH_GRADLE
 .aapt.nodeps: FORCE
-	cp $(gradle_dir)/app/intermediates/res/resources-official-australis-debug.ap_ gecko-nodeps.ap_
+	cp $(gradle_dir)/app/intermediates/res/resources-official-photon-debug.ap_ gecko-nodeps.ap_
 else
 # .aapt.nodeps: AndroidManifest.xml FORCE
 $(eval $(call aapt_command,.aapt.nodeps,AndroidManifest.xml FORCE,gecko-nodeps.ap_,gecko-nodeps/,gecko-nodeps/))
 endif
 
 # Override the Java settings with some specific android settings
 include $(topsrcdir)/config/android-common.mk
 

--- a/mobile/android/base/moz.build
+++ b/mobile/android/base/moz.build
@@ -1001,18 +1001,17 @@ gbjar.sources += ['java/org/mozilla/geck
     'widget/themed/ThemedImageView.java',
     'widget/themed/ThemedLinearLayout.java',
     'widget/themed/ThemedListView.java',
     'widget/themed/ThemedRelativeLayout.java',
     'widget/themed/ThemedTextSwitcher.java',
     'widget/themed/ThemedTextView.java',
     'widget/themed/ThemedView.java',
 ]]
-# The following sources are Photon specific, Eventually they should be merged into base/
-# when we are ready to drop Australis sources.
+# The following sources are Photon specific, Eventually they should be merged into base.
 gbjar.sources += ['../app/src/photon/java/org/mozilla/gecko/' + x for x in [
     'home/SearchEngineRow.java',
     'home/SuggestionItem.java',
     'skin/SkinConfig.java',
     'toolbar/BrowserToolbarTablet.java',
     'toolbar/BrowserToolbarTabletBase.java',
     'toolbar/ForwardButton.java',
     'toolbar/TabCounter.java',

--- a/mobile/android/gradle/with_gecko_binaries.gradle
+++ b/mobile/android/gradle/with_gecko_binaries.gradle
@@ -91,17 +91,17 @@ task checkAssetsExistInDistDir<< {
 task syncAssetsFromDistDir(type: Sync, dependsOn: checkAssetsExistInDistDir) {
     into("${project.buildDir}/generated/assets")
     from("${topobjdir}/dist/fennec/assets") {
         exclude 'omni.ja'
     }
 }
 
 ext.configureVariantWithGeckoBinaries = { variant ->
-    // Like 'localAustralis' or 'localOldAustralis'; may be null.
+    // Like 'localPhoton' or 'localOldPhoton'; may be null.
     def productFlavor = ""
     def productFlavorNames = variant.productFlavors.collect { it.name.capitalize() }
     if (!productFlavorNames.isEmpty()) {
         productFlavor = productFlavorNames.join()
         // Groovy's `uncapitilize` is not yet available.
         def c = productFlavor.toCharArray()
         c[0] = Character.toLowerCase(c[0])
         productFlavor = new String(c)

--- a/mobile/android/mach_commands.py
+++ b/mobile/android/mach_commands.py
@@ -48,17 +48,16 @@ class MachCommands(MachCommandBase):
 
 
     @SubCommand('android', 'test',
         """Run Android local unit tests.
         See https://developer.mozilla.org/en-US/docs/Mozilla/Android-specific_test_suites#android-test""")
     @CommandArgument('args', nargs=argparse.REMAINDER)
     def android_test(self, args):
         gradle_targets = [
-            'app:testOfficialAustralisDebugUnitTest',
             'app:testOfficialPhotonDebugUnitTest',
         ]
         ret = self.gradle(gradle_targets + ["--continue"] + args, verbose=True)
 
         # Findbug produces both HTML and XML reports.  Visit the
         # XML report(s) to report errors and link to the HTML
         # report(s) for human consumption.
         import itertools
@@ -68,18 +67,17 @@ class MachCommands(MachCommandBase):
             FileFinder,
         )
 
         if 'TASK_ID' in os.environ and 'RUN_ID' in os.environ:
             root_url = "https://queue.taskcluster.net/v1/task/{}/runs/{}/artifacts/public/android/unittest".format(os.environ['TASK_ID'], os.environ['RUN_ID'])
         else:
             root_url = os.path.join(self.topobjdir, 'gradle/build/mobile/android/app/reports/tests')
 
-        reports = ('officialAustralisDebug',
-                   'officialPhotonDebug',)
+        reports = ('officialPhotonDebug',)
         for report in reports:
             finder = FileFinder(os.path.join(self.topobjdir, 'gradle/build/mobile/android/app/test-results/', report))
             for p, _ in finder.find('TEST-*.xml'):
                 f = open(os.path.join(finder.base, p), 'rt')
                 tree = ET.parse(f)
                 root = tree.getroot()
 
                 print('SUITE-START | android-test | {} {}'.format(report, root.get('name')))
@@ -120,33 +118,31 @@ class MachCommands(MachCommandBase):
 
 
     @SubCommand('android', 'lint',
         """Run Android lint.
         See https://developer.mozilla.org/en-US/docs/Mozilla/Android-specific_test_suites#android-lint""")
     @CommandArgument('args', nargs=argparse.REMAINDER)
     def android_lint(self, args):
         gradle_targets = [
-            'app:lintOfficialAustralisDebug',
             'app:lintOfficialPhotonDebug',
         ]
         ret = self.gradle(gradle_targets + ["--continue"] + args, verbose=True)
 
         # Android Lint produces both HTML and XML reports.  Visit the
         # XML report(s) to report errors and link to the HTML
         # report(s) for human consumption.
         import xml.etree.ElementTree as ET
 
         if 'TASK_ID' in os.environ and 'RUN_ID' in os.environ:
             root_url = "https://queue.taskcluster.net/v1/task/{}/runs/{}/artifacts/public/android/lint".format(os.environ['TASK_ID'], os.environ['RUN_ID'])
         else:
             root_url = os.path.join(self.topobjdir, 'gradle/build/mobile/android/app/outputs')
 
-        reports = ('officialAustralisDebug',
-                   'officialPhotonDebug',)
+        reports = ('officialPhotonDebug',)
         for report in reports:
             f = open(os.path.join(self.topobjdir, 'gradle/build/mobile/android/app/outputs/lint-results-{}.xml'.format(report)), 'rt')
             tree = ET.parse(f)
             root = tree.getroot()
 
             print('SUITE-START | android-lint | {}'.format(report))
             for issue in root.findall("issue[@severity='Error']"):
                 # There's no particular advantage to formatting the
@@ -216,35 +212,32 @@ class MachCommands(MachCommandBase):
 
 
     @SubCommand('android', 'findbugs',
         """Run Android findbugs.
         See https://developer.mozilla.org/en-US/docs/Mozilla/Android-specific_test_suites#android-findbugs""")
     @CommandArgument('args', nargs=argparse.REMAINDER)
     def android_findbugs(self, dryrun=False, args=[]):
         gradle_targets = [
-            'app:findbugsXmlOfficialAustralisDebug',
-            'app:findbugsHtmlOfficialAustralisDebug',
             'app:findbugsXmlOfficialPhotonDebug',
             'app:findbugsHtmlOfficialPhotonDebug',
         ]
         ret = self.gradle(gradle_targets + ["--continue"] + args, verbose=True)
 
         # Findbug produces both HTML and XML reports.  Visit the
         # XML report(s) to report errors and link to the HTML
         # report(s) for human consumption.
         import xml.etree.ElementTree as ET
 
         if 'TASK_ID' in os.environ and 'RUN_ID' in os.environ:
             root_url = "https://queue.taskcluster.net/v1/task/{}/runs/{}/artifacts/public/artifacts/findbugs".format(os.environ['TASK_ID'], os.environ['RUN_ID'])
         else:
             root_url = os.path.join(self.topobjdir, 'gradle/build/mobile/android/app/outputs/findbugs')
 
-        reports = ('findbugs-officialAustralisDebug-output.xml',
-                   'findbugs-officialPhotonDebug-output.xml',)
+        reports = ('findbugs-officialPhotonDebug-output.xml',)
         for report in reports:
             try:
                 f = open(os.path.join(self.topobjdir, 'gradle/build/mobile/android/app/outputs/findbugs', report), 'rt')
             except IOError:
                 continue
 
             tree = ET.parse(f)
             root = tree.getroot()
@@ -271,22 +264,16 @@ class MachCommands(MachCommandBase):
         """Collect Android Gradle dependencies.
         See https://gecko.readthedocs.io/en/latest/build/buildsystem/toolchains.html#firefox-for-android-with-gradle""")
     @CommandArgument('args', nargs=argparse.REMAINDER)
     def android_gradle_dependencies(self, args):
         # The union, plus a bit more, of all of the Gradle tasks
         # invoked by the android-* automation jobs.
         gradle_targets = [
             'app:checkstyle',
-            'app:assembleOfficialAustralisRelease',
-            'app:assembleOfficialAustralisDebug',
-            'app:assembleOfficialAustralisDebugAndroidTest',
-            'app:findbugsXmlOfficialAustralisDebug',
-            'app:findbugsHtmlOfficialAustralisDebug',
-            'app:lintOfficialAustralisDebug',
             'app:assembleOfficialPhotonRelease',
             'app:assembleOfficialPhotonDebug',
             'app:assembleOfficialPhotonDebugAndroidTest',
             'app:findbugsXmlOfficialPhotonDebug',
             'app:findbugsHtmlOfficialPhotonDebug',
             'app:lintOfficialPhotonDebug',
             # Does not include Gecko binaries -- see mobile/android/gradle/with_gecko_binaries.gradle.
             'geckoview:assembleWithoutGeckoBinaries',

--- a/testing/mochitest/Makefile.in
+++ b/testing/mochitest/Makefile.in
@@ -20,17 +20,17 @@ libs::
 
 # On Android only, include a release signed Robocop APK in the test package.
 ifeq ($(MOZ_BUILD_APP),mobile/android)
 include $(topsrcdir)/config/android-common.mk
 
 ifndef MOZ_BUILD_MOBILE_ANDROID_WITH_GRADLE
 robocop_apk := $(topobjdir)/mobile/android/tests/browser/robocop/robocop-debug-unsigned-unaligned.apk
 else
-robocop_apk := $(topobjdir)/gradle/build/mobile/android/app/outputs/apk/app-official-australis-debug-androidTest-unaligned.apk
+robocop_apk := $(topobjdir)/gradle/build/mobile/android/app/outputs/apk/app-official-photon-debug-androidTest-unaligned.apk
 endif
 
 stage-package-android:
 	$(NSINSTALL) -D $(_DEST_DIR)
 	$(call RELEASE_SIGN_ANDROID_APK,$(robocop_apk),$(_DEST_DIR)/robocop.apk)
 
 stage-package: stage-package-android
 endif

--- a/testing/mochitest/mochitest_options.py
+++ b/testing/mochitest/mochitest_options.py
@@ -1027,17 +1027,17 @@ class AndroidArguments(ArgumentContainer
                     "Unable to find specified robocop .ini manifest '%s'" %
                     options.robocopIni)
             options.robocopIni = os.path.abspath(options.robocopIni)
 
             if not options.robocopApk and build_obj:
                 if build_obj.substs.get('MOZ_BUILD_MOBILE_ANDROID_WITH_GRADLE'):
                     options.robocopApk = os.path.join(build_obj.topobjdir, 'gradle', 'build',
                                                       'mobile', 'android', 'app', 'outputs', 'apk',
-                                                      'app-official-australis-debug-androidTest-'
+                                                      'app-official-photon-debug-androidTest-'
                                                       'unaligned.apk')
                 else:
                     options.robocopApk = os.path.join(build_obj.topobjdir, 'mobile', 'android',
                                                       'tests', 'browser',
                                                       'robocop', 'robocop-debug.apk')
 
         if options.robocopApk != "":
             if not os.path.exists(options.robocopApk):

--- a/toolkit/mozapps/installer/upload-files-APK.mk
+++ b/toolkit/mozapps/installer/upload-files-APK.mk
@@ -27,17 +27,17 @@ ifeq ($(MOZ_BUILD_APP),mobile/android)
 UPLOAD_EXTRA_FILES += robocop.apk
 
 # Robocop/Robotium tests, Android Background tests, and Fennec need to
 # be signed with the same key, which means release signing them all.
 
 ifndef MOZ_BUILD_MOBILE_ANDROID_WITH_GRADLE
 robocop_apk := $(topobjdir)/mobile/android/tests/browser/robocop/robocop-debug-unsigned-unaligned.apk
 else
-robocop_apk := $(topobjdir)/gradle/build/mobile/android/app/outputs/apk/app-official-australis-debug-androidTest-unaligned.apk
+robocop_apk := $(topobjdir)/gradle/build/mobile/android/app/outputs/apk/app-official-photon-debug-androidTest-unaligned.apk
 endif
 
 INNER_ROBOCOP_PACKAGE= \
   $(call RELEASE_SIGN_ANDROID_APK,$(robocop_apk),$(ABS_DIST)/robocop.apk)
 endif
 else
 INNER_ROBOCOP_PACKAGE=echo 'Testing is disabled - No Android Robocop for you'
 endif