diff --git a/apps/web/src/features/chat/components/message/ChatMessage.tsx b/apps/web/src/features/chat/components/message/ChatMessage.tsx
index e0d0185..4e8820b 100644
--- a/apps/web/src/features/chat/components/message/ChatMessage.tsx
+++ b/apps/web/src/features/chat/components/message/ChatMessage.tsx
@@ -91,6 +91,7 @@ function ChatMessageContent({
           kind={message.author.kind}
           name={message.author.name}
           agentRole={message.author.agentRole}
+          email={message.author.kind === "human" ? message.author.id : undefined}
         />
       }
       header={
diff --git a/apps/web/src/features/chat/components/message/MessageAvatar.tsx b/apps/web/src/features/chat/components/message/MessageAvatar.tsx
index 4800e7c..5efac1e 100644
--- a/apps/web/src/features/chat/components/message/MessageAvatar.tsx
+++ b/apps/web/src/features/chat/components/message/MessageAvatar.tsx
@@ -2,6 +2,7 @@ import { Icon } from "@tangent/ui-primitives/icon";
 import { cva } from "class-variance-authority";
 
 import type { AgentRole } from "@/features/chat/model/types";
+import { UserAvatar } from "@/features/user/components/UserAvatar";
 import { cn } from "@/shared/lib/utils";
 
 // Role-keyed avatar styling. The `agent`/`subagent` roles reuse the same
@@ -45,17 +46,27 @@ interface MessageAvatarProps {
   kind: "human" | "agent";
   name: string;
   agentRole?: AgentRole;
+  /** The human author's email, used to resolve a Gravatar image. */
+  email?: string;
 }
 
 /**
  * MessageAvatar — small circular badge conveying the message sender's kind
- * (human, prime agent, sub-agent). Styles a raw `<div>` (the sanctioned escape
- * hatch, like `StatusDot`/`UserAvatar`), so it is exempt from
- * tangle-ui/no-classname-on-primitives.
+ * (human, prime agent, sub-agent). Delegates to {@link UserAvatar}: human
+ * authors show their Gravatar, and everyone else (or a human without one) falls
+ * back to the role icon badge.
+ *
+ * Styles a raw `<div>` (the sanctioned escape hatch, like `StatusDot`), so it is
+ * exempt from `tangle-ui/no-classname-on-primitives`.
  */
-export function MessageAvatar({ kind, name, agentRole }: MessageAvatarProps) {
+export function MessageAvatar({
+  kind,
+  name,
+  agentRole,
+  email,
+}: MessageAvatarProps) {
   const role = avatarRole(kind, agentRole);
-  return (
+  const badge = (
     <div
       title={name}
       aria-label={name}
@@ -64,4 +75,10 @@ export function MessageAvatar({ kind, name, agentRole }: MessageAvatarProps) {
       <Icon name={AVATAR_ICONS[role]} size="xs" />
     </div>
   );
+
+  if (role !== "human" || !email?.trim().length) return badge;
+
+  return (
+    <UserAvatar email={email ?? ""} name={name} size="sm" fallback={badge} />
+  );
 }
diff --git a/apps/web/src/features/chat/components/message/ThinkingOnlyMessage.tsx b/apps/web/src/features/chat/components/message/ThinkingOnlyMessage.tsx
index 5662f3e..dc43e75 100644
--- a/apps/web/src/features/chat/components/message/ThinkingOnlyMessage.tsx
+++ b/apps/web/src/features/chat/components/message/ThinkingOnlyMessage.tsx
@@ -38,6 +38,7 @@ export function ThinkingOnlyMessage({
           kind={message.author.kind}
           name={message.author.name}
           agentRole={message.author.agentRole}
+          email={message.author.kind === "human" ? message.author.id : undefined}
         />
       }
       header={
diff --git a/apps/web/src/features/user/components/UserAvatar.tsx b/apps/web/src/features/user/components/UserAvatar.tsx
index ebb3812..e3be1df 100644
--- a/apps/web/src/features/user/components/UserAvatar.tsx
+++ b/apps/web/src/features/user/components/UserAvatar.tsx
@@ -1,26 +1,72 @@
-import type { UserIdentity } from "@tangent/shared/contracts";
+import { useQuery } from "@tanstack/react-query";
+import { cva } from "class-variance-authority";
+import type { ReactNode } from "react";
 
-import { userInitials } from "@/features/user/model/userDisplay";
+import { resolveGravatarUrl } from "@/features/user/model/gravatar";
+import { UserQueryKeys } from "@/features/user/model/userQueryKeys";
+import { Spinner } from "@tangent/ui-primitives/spinner";
+
+type AvatarSize = "sm" | "md";
+
+const avatarImageVariants = cva("shrink-0 rounded-full object-cover", {
+  variants: {
+    size: {
+      sm: "size-6",
+      md: "size-8",
+    },
+  },
+  defaultVariants: {
+    size: "md",
+  },
+});
+
+const AVATAR_SIZE_PX: Record<AvatarSize, number> = {
+  sm: 48,
+  md: 64,
+};
 
 interface UserAvatarProps {
-  user: UserIdentity;
+  /** Email to resolve a Gravatar for; empty skips the lookup and shows `fallback`. */
+  email: string;
+  /** Accessible label and tooltip for the image. */
+  name: string;
+  /** Badge shown when the email has no Gravatar or the lookup hasn't resolved. */
+  fallback: ReactNode;
+  size?: AvatarSize;
 }
 
 /**
- * UserAvatar — circular initials badge for the current user.
+ * UserAvatar — circular Gravatar image with a fallback badge. The existence
+ * check lives in the query (Gravatar 404s for emails without an avatar), so a
+ * missing avatar simply resolves to no URL and `fallback` renders — no separate
+ * error state or image `onError`.
  *
- * Styles a raw `<div>` (the sanctioned escape hatch, like `StatusDot`), so it
- * is exempt from `tangle-ui/no-classname-on-primitives`.
+ * Styles a raw `<img>` (the sanctioned escape hatch, like `StatusDot`), so it is
+ * exempt from `tangle-ui/no-classname-on-primitives`.
  */
-export function UserAvatar({ user }: UserAvatarProps) {
-  const fullName = `${user.first_name} ${user.last_name}`.trim();
+export function UserAvatar({
+  email,
+  name,
+  fallback,
+  size = "md",
+}: UserAvatarProps) {
+  const { data: src, isLoading } = useQuery({
+    queryKey: UserQueryKeys.Gravatar(email, AVATAR_SIZE_PX[size]),
+    queryFn: () => resolveGravatarUrl(email, AVATAR_SIZE_PX[size]),
+    enabled: email.trim().length > 0,
+    staleTime: Infinity,
+  });
+
+  if (isLoading) return <Spinner />;
+
+  if (!src) return <>{fallback}</>;
+
   return (
-    <div
-      title={fullName}
-      aria-label={fullName}
-      className="flex size-8 shrink-0 items-center justify-center rounded-full bg-secondary text-xs font-medium text-secondary-foreground"
-    >
-      {userInitials(user)}
-    </div>
+    <img
+      src={src}
+      title={name}
+      alt={name}
+      className={avatarImageVariants({ size })}
+    />
   );
 }
diff --git a/apps/web/src/features/user/components/UserInitialsBadge.tsx b/apps/web/src/features/user/components/UserInitialsBadge.tsx
new file mode 100644
index 0000000..f699986
--- /dev/null
+++ b/apps/web/src/features/user/components/UserInitialsBadge.tsx
@@ -0,0 +1,27 @@
+import type { UserIdentity } from "@tangent/shared/contracts";
+
+import { userInitials } from "@/features/user/model/userDisplay";
+
+interface UserInitialsBadgeProps {
+  user: UserIdentity;
+}
+
+/**
+ * UserInitialsBadge — circular initials badge, used as the {@link UserAvatar}
+ * fallback for the current user when no Gravatar exists.
+ *
+ * Styles a raw `<div>` (the sanctioned escape hatch, like `StatusDot`), so it is
+ * exempt from `tangle-ui/no-classname-on-primitives`.
+ */
+export function UserInitialsBadge({ user }: UserInitialsBadgeProps) {
+  const fullName = `${user.first_name} ${user.last_name}`.trim();
+  return (
+    <div
+      title={fullName}
+      aria-label={fullName}
+      className="flex size-8 shrink-0 items-center justify-center rounded-full bg-secondary text-xs font-medium text-secondary-foreground"
+    >
+      {userInitials(user)}
+    </div>
+  );
+}
diff --git a/apps/web/src/features/user/model/gravatar.ts b/apps/web/src/features/user/model/gravatar.ts
new file mode 100644
index 0000000..65814ec
--- /dev/null
+++ b/apps/web/src/features/user/model/gravatar.ts
@@ -0,0 +1,36 @@
+/**
+ * Builds the Gravatar image URL for an email using a SHA-256 hash (Gravatar
+ * accepts SHA-256, so we avoid an md5 dependency and Node `crypto`, neither of
+ * which work in the browser). `d=404` makes Gravatar 404 when no avatar exists.
+ * Returns `null` for an empty email.
+ */
+async function gravatarUrl(email: string, size: number): Promise<string | null> {
+  const normalized = email.trim().toLowerCase();
+  if (!normalized) return null;
+
+  const bytes = new TextEncoder().encode(normalized);
+  const digest = await crypto.subtle.digest("SHA-256", bytes);
+  const hash = Array.from(new Uint8Array(digest))
+    .map((b) => b.toString(16).padStart(2, "0"))
+    .join("");
+
+  return `https://www.gravatar.com/avatar/${hash}?s=${size}&d=404`;
+}
+
+/**
+ * Resolves the Gravatar URL for an email, returning it only when the avatar
+ * actually exists. Thanks to `d=404`, Gravatar 404s for emails with no avatar,
+ * so a failed fetch (or non-`ok` response) resolves to `null` and callers can
+ * show a fallback. Gravatar serves permissive CORS, so this cross-origin fetch
+ * is readable and its response is reused by the `<img>` from cache.
+ */
+export async function resolveGravatarUrl(
+  email: string,
+  size: number,
+): Promise<string | null> {
+  const url = await gravatarUrl(email, size);
+  if (!url) return null;
+
+  const res = await fetch(url);
+  return res.ok ? url : null;
+}
diff --git a/apps/web/src/features/user/model/userQueryKeys.ts b/apps/web/src/features/user/model/userQueryKeys.ts
index e78846a..01b7389 100644
--- a/apps/web/src/features/user/model/userQueryKeys.ts
+++ b/apps/web/src/features/user/model/userQueryKeys.ts
@@ -3,4 +3,6 @@
  */
 export const UserQueryKeys = {
   Me: () => ["me"] as const,
+  Gravatar: (email: string, size: number) =>
+    ["gravatar", email, size] as const,
 } as const;
diff --git a/apps/web/src/routes/layout/AppTopNav.tsx b/apps/web/src/routes/layout/AppTopNav.tsx
index a4ccb11..2cc8299 100644
--- a/apps/web/src/routes/layout/AppTopNav.tsx
+++ b/apps/web/src/routes/layout/AppTopNav.tsx
@@ -3,6 +3,7 @@ import { Text } from "@tangent/ui-primitives/typography";
 import { Link } from "@tanstack/react-router";
 
 import { UserAvatar } from "@/features/user/components/UserAvatar";
+import { UserInitialsBadge } from "@/features/user/components/UserInitialsBadge";
 import { useCurrentUser } from "@/features/user/hooks/useCurrentUser";
 import { TopNav, TopNavLink } from "@/shared/ui/patterns/top-nav";
 
@@ -17,6 +18,7 @@ import { ThemeMenu } from "./ThemeMenu";
  */
 export function AppTopNav() {
   const user = useCurrentUser();
+  const fullName = `${user.first_name} ${user.last_name}`.trim();
   return (
     <TopNav
       brand={
@@ -39,7 +41,11 @@ export function AppTopNav() {
       actions={
         <>
           <ThemeMenu />
-          <UserAvatar user={user} />
+          <UserAvatar
+            email={user.email}
+            name={fullName}
+            fallback={<UserInitialsBadge user={user} />}
+          />
         </>
       }
     />