diff --git a/automation/taskcluster/l10n/filter-release-translations.py b/automation/taskcluster/l10n/filter-release-translations.py
new file mode 100644
index 000000000..e1c3cdb8b
--- /dev/null
+++ b/automation/taskcluster/l10n/filter-release-translations.py
@@ -0,0 +1,50 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+"""
+This script takes the list of release locales defined in locales.py
+and removes all non-release translations from the application's
+resource folder.
+This script is run before building a release version so that
+those builds only contain locales we actually want to ship.
+"""
+
+import os
+import re
+import shutil
+
+from locales import RELEASE_LOCALES
+
+LANGUAGE_REGEX = re.compile('^[a-z]{2,3}$')
+LANGUAGE_REGION_REGEX = re.compile('^([a-z]{2})-r([A-Z]{2})$')
+
+# Get all resource directories that start with "values-" (and remove the "values-" prefix)
+resources_dir = os.path.join(os.path.dirname(__file__), '..', '..', '..', 'app', 'src', 'main', 'res')
+locale_dirs = [localeDir.replace('values-', '') for localeDir in os.listdir(resources_dir)
+               if os.path.isdir(os.path.join(resources_dir, localeDir))
+               and localeDir.startswith('values-')]
+
+# Remove everything that doesn't look like it's a resource folder for a specific language (e.g. sw600dp)
+locale_dirs = filter(lambda x: LANGUAGE_REGEX.match(x) or LANGUAGE_REGION_REGEX.match(x), locale_dirs)
+
+# Android prefixes regions with an "r" (de-rDE). Remove the prefix.
+locale_dirs = [item.replace('-r','-') for item in locale_dirs]
+
+# Now determine the list of locales that are not in our release list
+locales_to_remove = list(set(locale_dirs) - set(RELEASE_LOCALES))
+
+print "RELEASE LOCALES:", ", ".join(RELEASE_LOCALES)
+print "APP LOCALES:", ", ".join(locale_dirs)
+print "REMOVE:", ", ".join(locales_to_remove) if len(locales_to_remove) > 0 else "-Nothing-"
+
+# Remove unneeded resource folders
+for locale in locales_to_remove:
+    # Build resource folder names from locale: de -> values-de, de-DE -> vlaues-de-rDE
+    parts = locale.split("-")
+    folder = "values-" + (parts[0] if len(parts) == 1 else parts[0] + "-r" + parts[1])
+    path = os.path.join(resources_dir, folder)
+
+    print "* Removing: ", path
+    # This modifies source, which could cause problems if we ever start caching source
+    shutil.rmtree(path)
\ No newline at end of file
diff --git a/automation/taskcluster/l10n/locales.py b/automation/taskcluster/l10n/locales.py
new file mode 100644
index 000000000..5e2e80fe1
--- /dev/null
+++ b/automation/taskcluster/l10n/locales.py
@@ -0,0 +1,59 @@
+#!/usr/bin/python
+
+#  This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+from __future__ import absolute_import, print_function, unicode_literals
+
+import re
+
+OPEN_LOCALES = "locales = ["
+CLOSE_LOCALES = "]"
+
+def trim_to_locale(str):
+    match = re.search('\s*"([a-z]+-?[A-Z]*)",\s*', str)
+    if not match:
+        raise Exception("Failed parsing locale found in l10n.toml: " + str)
+    return match.group(1)
+
+
+# This file is a dumb parser that converts values from '/l10n.toml' to be easily consumed from
+# Python.
+#
+# 'l10n.toml' has a very simple structure, and it is reasonable to believe that this (very basic)
+# algorithm will continue to work as it is changed.
+#
+# Alternatives to custom parsing that were considered:
+# - Using standard library module --- none exists to parse TOML
+# - Importing a TOML parsing module --- introduces an additional build step, complexity, and
+#   security risk
+# - Vendoring a TOML module --- large amount of code given the use case. Introduces a security
+#   risk
+def get_release_locales():
+    with open(r"l10n.toml") as f:
+        file = f.read().splitlines()
+
+    locales_opened = False
+    locales_closed = False
+
+    found_locales = []
+
+    for line in file:
+        if line == OPEN_LOCALES:
+            locales_opened = True
+        elif line == CLOSE_LOCALES:
+            locales_closed = True
+            break
+        elif locales_opened:
+            found_locales.append(trim_to_locale(line))
+
+    if locales_opened == False:
+        raise Exception("Could not find `locales` open in l10n.toml")
+    if locales_closed == False:
+        raise Exception("Could not find `locales` close in l10n.toml")
+
+    return found_locales
+
+
+RELEASE_LOCALES = get_release_locales()
diff --git a/taskcluster/ci/build/kind.yml b/taskcluster/ci/build/kind.yml
index 5cc328eed..c8c28f27c 100644
--- a/taskcluster/ci/build/kind.yml
+++ b/taskcluster/ci/build/kind.yml
@@ -100,6 +100,7 @@ jobs:
             release-type: beta
         include-release-version: true
         include-shippable-secrets: true
+        filter-incomplete-translations: true
         run:
             geckoview-engine: geckoBeta
             gradle-build-type: fenixBeta
@@ -112,6 +113,7 @@ jobs:
             release-type: production
         include-release-version: true
         include-shippable-secrets: true
+        filter-incomplete-translations: true
         run:
             geckoview-engine: geckoBeta
             gradle-build-type: fenixProduction
@@ -134,9 +136,11 @@ jobs:
         attributes:
             # TODO replace `nightly: true` by `release-type: beta` once the data migration
             # testing is over
+            # TODO when making the above change, uncomment `filter-incomplete-translations: true`
             nightly: true
         include-release-version: true
         include-shippable-secrets: true
+#        filter-incomplete-translations: true
         run:
             geckoview-engine: geckoBeta
             gradle-build-type: fennecBeta
@@ -147,9 +151,11 @@ jobs:
         attributes:
             # TODO replace `nightly: true` by `release-type: production` once the data migration
             # testing is over
+            # TODO when making the above change, uncomment `filter-incomplete-translations: true`
             nightly: true
         include-release-version: true
         include-shippable-secrets: true
+#        filter-incomplete-translations: true
         run:
             geckoview-engine: geckoBeta
             gradle-build-type: fennecProduction
diff --git a/taskcluster/fenix_taskgraph/transforms/build.py b/taskcluster/fenix_taskgraph/transforms/build.py
index bd372e80b..1973761be 100644
--- a/taskcluster/fenix_taskgraph/transforms/build.py
+++ b/taskcluster/fenix_taskgraph/transforms/build.py
@@ -125,3 +125,13 @@ def add_artifacts(config, tasks):
                 apks[apk["abi"]] = apk_name
 
         yield task
+
+
+@transforms.add
+def filter_incomplete_translation(config, tasks):
+    for task in tasks:
+        if task.pop("filter-incomplete-translations", False):
+            # filter-release-translations modifies source, which could cause problems if we ever start caching source
+            pre_gradlew = task["run"].setdefault("pre-gradlew", [])
+            pre_gradlew.append(["python", "automation/taskcluster/l10n/filter-release-translations.py"])
+        yield task