diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index be596ff7..b146acd3 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -81,3 +81,25 @@ Changelog and release notes are generated with
 
 By contributing, you agree that your contributions are dual-licensed under
 **MIT OR Apache-2.0**, matching the project.
+
+## Developer Certificate of Origin (DCO)
+
+All contributions must be signed off under the
+[Developer Certificate of Origin](./DCO) (DCO 1.1) — signing off certifies that
+you wrote the change, or otherwise have the right to submit it under the
+project's license. Add a sign-off line to every commit with:
+
+```sh
+git commit -s
+```
+
+which appends a trailer using your `git config` identity:
+
+```
+Signed-off-by: Your Name <you@example.com>
+```
+
+A DCO check runs on every pull request, so commits missing a valid
+`Signed-off-by` will be flagged. To fix a commit you already made, use
+`git commit --amend -s`; to sign off a range, `git rebase --signoff <base>`.
+(This is separate from commit *signing* — `git commit -s -S` does both.)
diff --git a/DCO b/DCO
new file mode 100644
index 00000000..49b8cb05
--- /dev/null
+++ b/DCO
@@ -0,0 +1,34 @@
+Developer Certificate of Origin
+Version 1.1
+
+Copyright (C) 2004, 2006 The Linux Foundation and its contributors.
+
+Everyone is permitted to copy and distribute verbatim copies of this
+license document, but changing it is not allowed.
+
+
+Developer's Certificate of Origin 1.1
+
+By making a contribution to this project, I certify that:
+
+(a) The contribution was created in whole or in part by me and I
+    have the right to submit it under the open source license
+    indicated in the file; or
+
+(b) The contribution is based upon previous work that, to the best
+    of my knowledge, is covered under an appropriate open source
+    license and I have the right under that license to submit that
+    work with modifications, whether created in whole or in part
+    by me, under the same open source license (unless I am
+    permitted to submit under a different license), as indicated
+    in the file; or
+
+(c) The contribution was provided directly to me by some other
+    person who certified (a), (b) or (c) and I have not modified
+    it.
+
+(d) I understand and agree that this project and the contribution
+    are public and that a record of the contribution (including all
+    personal information I submit with it, including my sign-off) is
+    maintained indefinitely and may be redistributed consistent with
+    this project or the open source license(s) involved.