diff --git a/src/app/insights/page-client.tsx b/src/app/insights/page-client.tsx
index de0233ea3..fb3c162be 100644
--- a/src/app/insights/page-client.tsx
+++ b/src/app/insights/page-client.tsx
@@ -7,6 +7,7 @@ import Link from "next/link";
 import { SlidersHorizontal, TrendingUp } from "lucide-react";
 
 import { useAuth } from "@/hooks/use-auth";
+import { accountName } from "@/lib/account-name";
 import { queryKeys } from "@/lib/query-keys";
 import { apiGet } from "@/lib/api/api-fetch";
 // Bare number — its own React- and label-map-free module, so importing it here
@@ -419,10 +420,9 @@ export default function InsightsPageClient() {
   // boundary hydrates, and a greeting that personalises during the
   // hydration render disagrees with the name-less SSR text — React
   // #418. See `useMounted`.
+  const shownName = user ? accountName(user).trim() : "";
   const heroGreetingName =
-    mounted && user?.username?.trim() && user.username.trim().length > 0
-      ? user.username.split(/\s+/)[0]
-      : null;
+    mounted && shownName.length > 0 ? shownName.split(/\s+/)[0] : null;
   // The advisor read only fires while the briefing is available, so with it
   // unavailable these stay null: the hero keeps its fallback subtitle and the
   // trends row its built-in captions.
diff --git a/src/components/dashboard/dashboard-header.tsx b/src/components/dashboard/dashboard-header.tsx
index 1a7308bff..c4e70a63b 100644
--- a/src/components/dashboard/dashboard-header.tsx
+++ b/src/components/dashboard/dashboard-header.tsx
@@ -32,6 +32,7 @@ import {
 import { PageHeader } from "@/components/ui/page-header";
 import { useTranslations } from "@/lib/i18n/context";
 import { useAuth } from "@/hooks/use-auth";
+import { accountName } from "@/lib/account-name";
 import { useMounted } from "@/hooks/use-mounted";
 import { useRecordCapabilities } from "@/hooks/use-record-capabilities";
 import { hourInTz } from "@/lib/tz/format";
@@ -143,7 +144,7 @@ export function DashboardHeader({
   const greeting = greetingLine({
     greeting: timeGreeting,
     known: mounted && user != null,
-    name: user?.username?.trim() ? user.username : null,
+    name: user ? accountName(user).trim() || null : null,
     createdAt: user?.createdAt,
   });
   const welcomeText = t(greeting.key, greeting.values);
diff --git a/src/components/layout/__tests__/sidebar-nav.test.tsx b/src/components/layout/__tests__/sidebar-nav.test.tsx
index c6d519608..a79eda4d1 100644
--- a/src/components/layout/__tests__/sidebar-nav.test.tsx
+++ b/src/components/layout/__tests__/sidebar-nav.test.tsx
@@ -18,6 +18,7 @@ const mockUserRef = {
   value: {
     id: "u1",
     username: "testuser",
+    displayName: null as string | null,
     email: "user@example.com",
     role: "USER" as "USER" | "ADMIN",
     avatarUrl: null,
@@ -119,6 +120,25 @@ const GATED_HREFS = [
   "/achievements",
 ] as const;
 
+describe("<SidebarNav> account identity", () => {
+  afterEach(() => {
+    mockUserRef.value = { ...mockUserRef.value, displayName: null };
+  });
+
+  it("names the account by its display name when one is set", () => {
+    mockUserRef.value = { ...mockUserRef.value, displayName: "Jane Doe" };
+    const html = render();
+    expect(html).toContain(">Jane Doe</p>");
+    expect(html).toContain(">JD</span>");
+    expect(html).not.toContain(">testuser</p>");
+  });
+
+  it("falls back to the username without a display name", () => {
+    const html = render();
+    expect(html).toContain(">testuser</p>");
+  });
+});
+
 describe("<SidebarNav> first-paint fail-closed module gate (v1.25.12)", () => {
   it("renders core destinations on first paint regardless of the module map", () => {
     const maps: Record<string, boolean>[] = [
diff --git a/src/components/layout/sidebar-nav.tsx b/src/components/layout/sidebar-nav.tsx
index ff2c62444..28062cbb8 100644
--- a/src/components/layout/sidebar-nav.tsx
+++ b/src/components/layout/sidebar-nav.tsx
@@ -40,6 +40,7 @@ import {
 import { cn } from "@/lib/utils";
 import { Logo } from "@/components/ui/logo";
 import { useAuth, useLogout } from "@/hooks/use-auth";
+import { accountName } from "@/lib/account-name";
 import { useIsMobile } from "@/hooks/use-is-mobile";
 import { useNavModules } from "@/hooks/use-nav-modules";
 import { useMounted } from "@/hooks/use-mounted";
@@ -153,6 +154,7 @@ function SidebarUserSection({ collapsed }: { collapsed: boolean }) {
   const sharedRecord = user?.accountAccess?.active != null;
 
   if (!user) return null;
+  const name = accountName(user);
 
   const themeIcon =
     theme === "system" ? (
@@ -166,13 +168,13 @@ function SidebarUserSection({ collapsed }: { collapsed: boolean }) {
   const identityBlock = (
     <>
       <Avatar className="h-9 w-9 shrink-0">
-        {avatarUrl && <AvatarImage src={avatarUrl} alt={user.username} />}
+        {avatarUrl && <AvatarImage src={avatarUrl} alt={name} />}
         <AvatarFallback className="bg-primary/15 text-primary text-xs font-medium">
-          {getInitials(user.username)}
+          {getInitials(name)}
         </AvatarFallback>
       </Avatar>
       <div className="min-w-0 flex-1">
-        <p className="truncate text-sm font-semibold">{user.username}</p>
+        <p className="truncate text-sm font-semibold">{name}</p>
         {user.email && (
           <p className="text-muted-foreground truncate text-xs">{user.email}</p>
         )}
@@ -282,11 +284,9 @@ function SidebarUserSection({ collapsed }: { collapsed: boolean }) {
             <DropdownMenuTrigger className="hover:bg-accent focus-visible:ring-ring/50 shrink-0 rounded-md p-1.5 transition-colors focus:outline-none focus-visible:ring-[3px]">
               <span className="sr-only">{t("nav.userMenu")}</span>
               <Avatar className="h-8 w-8" aria-hidden="true">
-                {avatarUrl && (
-                  <AvatarImage src={avatarUrl} alt={user.username} />
-                )}
+                {avatarUrl && <AvatarImage src={avatarUrl} alt={name} />}
                 <AvatarFallback className="bg-primary/15 text-primary text-xs font-medium">
-                  {getInitials(user.username)}
+                  {getInitials(name)}
                 </AvatarFallback>
               </Avatar>
             </DropdownMenuTrigger>
@@ -311,13 +311,13 @@ function SidebarUserSection({ collapsed }: { collapsed: boolean }) {
           label={t("nav.accountSettings")}
         >
           <Avatar className="h-8 w-8 shrink-0" aria-hidden="true">
-            {avatarUrl && <AvatarImage src={avatarUrl} alt={user.username} />}
+            {avatarUrl && <AvatarImage src={avatarUrl} alt={name} />}
             <AvatarFallback className="bg-primary/15 text-primary text-xs font-medium">
-              {getInitials(user.username)}
+              {getInitials(name)}
             </AvatarFallback>
           </Avatar>
           <div className="min-w-0 flex-1">
-            <p className="truncate text-sm font-medium">{user.username}</p>
+            <p className="truncate text-sm font-medium">{name}</p>
             {user.email && (
               <p className="text-muted-foreground truncate text-xs">
                 {user.email}
diff --git a/src/components/layout/top-bar.tsx b/src/components/layout/top-bar.tsx
index 23988f100..4d499d1a2 100644
--- a/src/components/layout/top-bar.tsx
+++ b/src/components/layout/top-bar.tsx
@@ -26,6 +26,7 @@ import { Avatar, AvatarFallback, AvatarImage } from "@/components/ui/avatar";
 import { Skeleton } from "@/components/ui/skeleton";
 import Link from "next/link";
 import { useAuth, useLogout } from "@/hooks/use-auth";
+import { accountName } from "@/lib/account-name";
 import { useRecordCapabilities } from "@/hooks/use-record-capabilities";
 import { useTheme } from "@/components/providers";
 import { useTranslations } from "@/lib/i18n/context";
@@ -143,13 +144,13 @@ export function TopBar() {
               <span className="sr-only">{t("nav.userMenu")}</span>
               <Avatar className="size-7" aria-hidden="true">
                 {avatarUrl && (
-                  <AvatarImage src={avatarUrl} alt={user.username} />
+                  <AvatarImage src={avatarUrl} alt={accountName(user)} />
                 )}
                 <AvatarFallback className="bg-primary/15 text-primary text-xs font-medium">
-                  {getInitials(user.username)}
+                  {getInitials(accountName(user))}
                 </AvatarFallback>
               </Avatar>
-              <span className="hidden sm:inline">{user.username}</span>
+              <span className="hidden sm:inline">{accountName(user)}</span>
               <ChevronDown className="h-3 w-3 opacity-60" />
             </DropdownMenuTrigger>
             <DropdownMenuContent align="end" className="w-60">
diff --git a/src/lib/__tests__/account-name.test.ts b/src/lib/__tests__/account-name.test.ts
new file mode 100644
index 000000000..3d080ebb1
--- /dev/null
+++ b/src/lib/__tests__/account-name.test.ts
@@ -0,0 +1,21 @@
+import { describe, expect, it } from "vitest";
+
+import { accountName } from "../account-name";
+
+describe("accountName", () => {
+  it("names the account by its display name when one is set", () => {
+    expect(accountName({ username: "jdoe", displayName: "Jane" })).toBe("Jane");
+  });
+
+  it("trims the display name it shows", () => {
+    expect(accountName({ username: "jdoe", displayName: "  Jane  " })).toBe(
+      "Jane",
+    );
+  });
+
+  it("falls back to the username when the display name is empty or absent", () => {
+    expect(accountName({ username: "jdoe", displayName: "   " })).toBe("jdoe");
+    expect(accountName({ username: "jdoe", displayName: null })).toBe("jdoe");
+    expect(accountName({ username: "jdoe" })).toBe("jdoe");
+  });
+});
diff --git a/src/lib/account-name.ts b/src/lib/account-name.ts
new file mode 100644
index 000000000..2340acaa6
--- /dev/null
+++ b/src/lib/account-name.ts
@@ -0,0 +1,13 @@
+/**
+ * The name the app shows and addresses an account by: the display name when
+ * one is set, the username otherwise. Greetings, the top bar and the sidebar
+ * all read it here, so the display name edited on the profile card reaches
+ * every surface that names the account.
+ */
+export function accountName(user: {
+  username: string;
+  displayName?: string | null;
+}): string {
+  const displayName = user.displayName?.trim();
+  return displayName ? displayName : user.username;
+}