diff --git a/docs/docs/api.md b/docs/docs/api.md
index 1cea6027..667c68b8 100644
--- a/docs/docs/api.md
+++ b/docs/docs/api.md
@@ -34,6 +34,18 @@ response was a 4xx or 5xx.)
 
 ## Endpoints
 
+### `GET /v0/user/[username]`
+
+Gets a user by their username. Remember that usernames may change.
+
+Requires no authorization.
+
+### `GET /v0/user/by-id/[id]`
+
+Gets a user by their unique ID. Many other API endpoints return this as the `userId`.
+
+Requires no authorization.
+
 ### `GET /v0/markets`
 
 Lists all markets, ordered by creation date descending.
@@ -627,6 +639,7 @@ Requires no authorization.
 
 ## Changelog
 
+- 2022-07-15: Add user by username and user by ID APIs
 - 2022-06-08: Add paging to markets endpoint
 - 2022-06-05: Add new authorized write endpoints
 - 2022-02-28: Add `resolutionTime` to markets, change `closeTime` definition
diff --git a/web/pages/api/v0/user/[username]/index.ts b/web/pages/api/v0/user/[username]/index.ts
new file mode 100644
index 00000000..58daffcd
--- /dev/null
+++ b/web/pages/api/v0/user/[username]/index.ts
@@ -0,0 +1,19 @@
+import { NextApiRequest, NextApiResponse } from 'next'
+import { getUserByUsername } from 'web/lib/firebase/users'
+import { applyCorsHeaders, CORS_UNRESTRICTED } from 'web/lib/api/cors'
+import { LiteUser, ApiError, toLiteUser } from '../../_types'
+
+export default async function handler(
+  req: NextApiRequest,
+  res: NextApiResponse<LiteUser | ApiError>
+) {
+  await applyCorsHeaders(req, res, CORS_UNRESTRICTED)
+  const { username } = req.query
+  const user = await getUserByUsername(username as string)
+  if (!user) {
+    res.status(404).json({ error: 'User not found' })
+    return
+  }
+  res.setHeader('Cache-Control', 'no-cache')
+  return res.status(200).json(toLiteUser(user))
+}
diff --git a/web/pages/api/v0/user/by-id/[id].ts b/web/pages/api/v0/user/by-id/[id].ts
new file mode 100644
index 00000000..6ed67d1c
--- /dev/null
+++ b/web/pages/api/v0/user/by-id/[id].ts
@@ -0,0 +1,19 @@
+import { NextApiRequest, NextApiResponse } from 'next'
+import { getUser } from 'web/lib/firebase/users'
+import { applyCorsHeaders, CORS_UNRESTRICTED } from 'web/lib/api/cors'
+import { LiteUser, ApiError, toLiteUser } from '../../_types'
+
+export default async function handler(
+  req: NextApiRequest,
+  res: NextApiResponse<LiteUser | ApiError>
+) {
+  await applyCorsHeaders(req, res, CORS_UNRESTRICTED)
+  const { id } = req.query
+  const user = await getUser(id as string)
+  if (!user) {
+    res.status(404).json({ error: 'User not found' })
+    return
+  }
+  res.setHeader('Cache-Control', 'no-cache')
+  return res.status(200).json(toLiteUser(user))
+}