diff --git a/build/sparse-profiles/sphinx-docs b/build/sparse-profiles/sphinx-docs
index 6a2451057e15..6b82644f3985 100644
--- a/build/sparse-profiles/sphinx-docs
+++ b/build/sparse-profiles/sphinx-docs
@@ -28,3 +28,9 @@ glob:**/moz.build
 
 # Read to set the version of the docs.
 path:config/milestone.txt
+
+# metrics.yaml and pings.yaml files (and their index) are needed to generate
+# Glean autodocs
+glob:**/metrics.yaml
+glob:**/pings.yaml
+path:toolkit/components/glean/metrics_index.py
diff --git a/docs/conf.py b/docs/conf.py
index b2ab3e0c06fa..8224f43977a9 100644
--- a/docs/conf.py
+++ b/docs/conf.py
@@ -27,6 +27,7 @@ EXTRA_PATHS = (
     "third_party/python/futures",
     "third_party/python/jsmin",
     "third_party/python/which",
+    "toolkit/components/glean/sphinx",
 )
 
 sys.path[:0] = [os.path.join(topsrcdir, p) for p in EXTRA_PATHS]
@@ -46,6 +47,7 @@ extensions = [
     "recommonmark",
     "sphinx_copybutton",
     "sphinx_markdown_tables",
+    "glean",
 ]
 
 # JSDoc must run successfully for dirs specified, so running
diff --git a/docs/config.yml b/docs/config.yml
index 6da762b27771..aa5664c11e2c 100644
--- a/docs/config.yml
+++ b/docs/config.yml
@@ -48,6 +48,8 @@ categories:
         - python
     fennec_doc:
         - mobile/android
+    metrics_doc:
+        - metrics
 
 redirects:
     browser/browser: browser
diff --git a/docs/index.rst b/docs/index.rst
index 7cf26ce71322..460a2c9e2b60 100644
--- a/docs/index.rst
+++ b/docs/index.rst
@@ -44,6 +44,12 @@ Firefox Source Tree Documentation
 
    {python_doc}
 
+.. toctree::
+   :caption: Metrics Collected in Firefox
+   :maxdepth: 1
+
+   {metrics_doc}
+
 
 Indices and tables
 ==================
diff --git a/toolkit/components/glean/build_scripts/glean_parser_ext/run_glean_parser.py b/toolkit/components/glean/build_scripts/glean_parser_ext/run_glean_parser.py
index 59750250326d..7abb7155b79e 100644
--- a/toolkit/components/glean/build_scripts/glean_parser_ext/run_glean_parser.py
+++ b/toolkit/components/glean/build_scripts/glean_parser_ext/run_glean_parser.py
@@ -11,11 +11,23 @@ from glean_parser import lint, parser, util
 from pathlib import Path
 
 
-def main(output_fd, *metrics_yamls):
+def main(output_fd, metrics_index_path, which_array):
+
+    # Source the list of input files from `metrics_index.py`
+    sys.path.append(str(Path(metrics_index_path).parent))
+    from metrics_index import METRICS, PINGS
+    if which_array == 'METRICS':
+        input_files = METRICS
+    elif which_array == 'PINGS':
+        input_files = PINGS
+    else:
+        print("Build system's asking for unknown array {}".format(which_array))
+        sys.exit(1)
+
     # Derived heavily from glean_parser.translate.translate.
     # Adapted to how mozbuild sends us a fd.
     options = {"allow_reserved": False}
-    input_files = [Path(x) for x in metrics_yamls]
+    input_files = [Path(x) for x in input_files]
 
     all_objs = parser.parse_objects(input_files, options)
     if util.report_validation_errors(all_objs):
diff --git a/toolkit/components/glean/docs/new_definitions_file.md b/toolkit/components/glean/docs/new_definitions_file.md
index ba39e03b9d5b..3dbcd4657034 100644
--- a/toolkit/components/glean/docs/new_definitions_file.md
+++ b/toolkit/components/glean/docs/new_definitions_file.md
@@ -27,13 +27,16 @@ But where can you find `metrics.yaml` or `pings.yaml`?
 If you're not the first person in your component to ask that question,
 the answer is likely "in the root of your component".
 Look for the definitions files near to where you are instrumenting your code.
+Or you can look in
+`toolkit/components/glean/metrics_index.py`
+to see the list of all currently-known definitions files.
 
 If you _are_ the first person in your component to ask that question,
 you get to choose where to start them!
 We recommend adding them in the root of your component, next to a `moz.build`.
 
-When you do so, be sure to edit `toolkit/components/glean/moz.build`,
-adding your definitions files to the `GeneratedFile` directives therein.
+When you do so, be sure to edit `toolkit/components/glean/metrics_index.py`,
+adding your definitions files to the Python lists therein.
 If you don't, no API will be generated for your metrics and your build will fail.
 
 In addition, do not forget to file a bug in `Data Platform and Tools :: General`
diff --git a/toolkit/components/glean/metrics_index.py b/toolkit/components/glean/metrics_index.py
new file mode 100644
index 000000000000..0bf70cc98d23
--- /dev/null
+++ b/toolkit/components/glean/metrics_index.py
@@ -0,0 +1,17 @@
+# -*- coding: utf-8 -*-
+
+# 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/.
+
+# The list of all Glean metrics.yaml files, relative to the top src dir.
+# New additions should be added to the bottom of the list.
+METRICS = [
+    'toolkit/components/glean/metrics.yaml',
+]
+
+# The list of all Glean pings.yaml files, relative to the top src dir.
+# New additions should be added to the bottom of the list.
+PINGS = [
+    'toolkit/components/glean/pings.yaml',
+]
diff --git a/toolkit/components/glean/moz.build b/toolkit/components/glean/moz.build
index d7aa07f01ab8..1372aca00881 100644
--- a/toolkit/components/glean/moz.build
+++ b/toolkit/components/glean/moz.build
@@ -30,11 +30,13 @@ if CONFIG['MOZ_GLEAN']:
 
     GeneratedFile('api/src/metrics.rs',
                   script='build_scripts/glean_parser_ext/run_glean_parser.py',
-                  inputs=['metrics.yaml'])
+                  flags=['METRICS'],
+                  inputs=['metrics_index.py'])
 
     GeneratedFile('api/src/pings.rs',
                   script='build_scripts/glean_parser_ext/run_glean_parser.py',
-                  inputs=['pings.yaml'])
+                  flags=['PINGS'],
+                  inputs=['metrics_index.py'])
 
     DIRS += [
         'aboutGlean',
diff --git a/toolkit/components/glean/sphinx/glean.py b/toolkit/components/glean/sphinx/glean.py
new file mode 100644
index 000000000000..7273de3bdf48
--- /dev/null
+++ b/toolkit/components/glean/sphinx/glean.py
@@ -0,0 +1,26 @@
+# 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/.
+
+import os
+from pathlib import Path
+import sys
+
+
+def setup(app):
+    from moztreedocs import manager
+
+    # Import the list of metrics and ping files
+    glean_dir = os.path.abspath(os.path.join(os.path.dirname(__file__), os.path.pardir))
+    sys.path.append(glean_dir)
+    from metrics_index import METRICS, PINGS
+    input_files = [Path(os.path.join(manager.topsrcdir, x)) for x in METRICS]
+    input_files += [Path(os.path.join(manager.topsrcdir, x)) for x in PINGS]
+
+    # Generate the autodocs.
+    from glean_parser import translate
+    out_path = Path(os.path.join(manager.staging_dir, 'metrics'))
+    translate.translate(input_files, 'markdown', out_path, {'project_title': 'Firefox'})
+
+    # Rename the generated docfile to index so Sphinx finds it
+    os.rename(os.path.join(out_path, 'metrics.md'), os.path.join(out_path, 'index.md'))