diff --git a/src/admin/site-admin-sheet.tsx b/src/admin/site-admin-sheet.tsx
new file mode 100644
index 0000000..e9e8096
--- /dev/null
+++ b/src/admin/site-admin-sheet.tsx
@@ -0,0 +1,256 @@
+import { useState } from 'react';
+import { Alert as RNAlert, Pressable, View } from 'react-native';
+import { useQueryClient } from '@tanstack/react-query';
+
+import {
+  resetPasswordAdminUsersUserIdResetPasswordPost,
+  updateUserAdminUsersUserIdPatch,
+  useListUsersAdminUsersGet,
+} from '@/api/generated/endpoints/admin/admin';
+import type { AdminUserRead, UserMe } from '@/api/generated/models';
+import { errorDetail } from '@/api/errors';
+import { AppText, Alert, Avatar, Button, Card, Field } from '@/ui/primitives';
+import { Sheet } from '@/ui/sheet';
+import { useDebouncedValue } from '@/ui/use-debounced-value';
+import { useTokens } from '@/ui/theme';
+
+/**
+ * The user directory, per `docs/design/mobile/154-site-admin.svg`.
+ *
+ * Site admins only; the server refuses everyone else, and the entry point is
+ * hidden for them so there is nothing to discover that would be denied.
+ *
+ * Every guard is the server's -- you cannot deactivate or demote yourself, and
+ * the last active site admin is protected. Those two are checked here as well,
+ * not to enforce them but so the action is explained rather than merely refused.
+ */
+const PAGE = 25;
+
+export function SiteAdminSheet({
+  visible,
+  onClose,
+  user,
+}: {
+  visible: boolean;
+  onClose: () => void;
+  user: UserMe | null;
+}) {
+  const t = useTokens();
+  const queryClient = useQueryClient();
+
+  const [query, setQuery] = useState('');
+  const [limit, setLimit] = useState(PAGE);
+  const [error, setError] = useState<string | null>(null);
+  const [resetting, setResetting] = useState<AdminUserRead | null>(null);
+
+  const settled = useDebouncedValue(query.trim(), 300);
+  const users = useListUsersAdminUsersGet(
+    { q: settled || undefined, limit, offset: 0 },
+    { query: { enabled: visible } },
+  );
+
+  const items = users.data?.items ?? [];
+  const total = users.data?.total ?? 0;
+  const activeAdmins = items.filter((row) => row.is_site_admin && row.is_active).length;
+
+  async function run(action: () => Promise<void>, fallback: string) {
+    setError(null);
+    try {
+      await action();
+      await queryClient.invalidateQueries({ queryKey: ['/admin/users'] });
+    } catch (err) {
+      setError(errorDetail(err, fallback));
+    }
+  }
+
+  function manage(row: AdminUserRead) {
+    const isSelf = row.id === user?.id;
+    // The page shows one page at a time, so this count is only a hint -- the
+    // server has the real answer and will refuse regardless.
+    const lastAdmin = row.is_site_admin && row.is_active && activeAdmins <= 1;
+
+    const options: Parameters<typeof RNAlert.alert>[2] = [
+      { text: 'Cancel', style: 'cancel' },
+    ];
+
+    if (!isSelf && !lastAdmin) {
+      options.push({
+        text: row.is_site_admin ? 'Revoke site admin' : 'Grant site admin',
+        onPress: () =>
+          void run(
+            () =>
+              updateUserAdminUsersUserIdPatch(row.id, {
+                is_site_admin: !row.is_site_admin,
+              }).then(() => undefined),
+            'Could not change that role.',
+          ),
+      });
+    }
+
+    options.push({
+      text: 'Set a password',
+      onPress: () => setResetting(row),
+    });
+
+    if (!isSelf && !lastAdmin) {
+      options.push({
+        text: row.is_active ? 'Deactivate' : 'Reactivate',
+        style: row.is_active ? 'destructive' : 'default',
+        onPress: () =>
+          void run(
+            () =>
+              updateUserAdminUsersUserIdPatch(row.id, {
+                is_active: !row.is_active,
+              }).then(() => undefined),
+            'Could not change that account.',
+          ),
+      });
+    }
+
+    RNAlert.alert(
+      row.full_name,
+      isSelf
+        ? 'You cannot deactivate or demote your own account.'
+        : lastAdmin
+          ? 'This is the last active site admin — promote somebody else first.'
+          : row.email,
+      options,
+    );
+  }
+
+  if (!visible) return null;
+
+  return (
+    <Sheet visible onClose={onClose} title="All users">
+      <View style={{ gap: 12, paddingBottom: 12 }}>
+        {error ? <Alert>{error}</Alert> : null}
+
+        <Field
+          label="Search"
+          value={query}
+          onChangeText={setQuery}
+          placeholder="Name, username or email"
+          autoCapitalize="none"
+          autoCorrect={false}
+        />
+
+        {items.map((row) => (
+          <Pressable
+            key={row.id}
+            accessibilityRole="button"
+            accessibilityLabel={`Manage ${row.full_name}`}
+            onPress={() => manage(row)}
+          >
+            <Card
+              style={{
+                flexDirection: 'row',
+                alignItems: 'center',
+                gap: 12,
+                padding: 12,
+                // A deactivated account is still listed, because reactivating
+                // it is the whole point of it being here.
+                opacity: row.is_active ? 1 : 0.55,
+              }}
+            >
+              <Avatar name={row.full_name} color={row.avatar_color} size={32} />
+              <View style={{ flex: 1, gap: 2 }}>
+                <AppText variant="body" numberOfLines={1} style={{ fontSize: 14 }}>
+                  {row.full_name}
+                  {row.id === user?.id ? ' (you)' : ''}
+                </AppText>
+                <AppText variant="hint" numberOfLines={1}>
+                  {row.email} · {row.team_count} team{row.team_count === 1 ? '' : 's'}
+                </AppText>
+              </View>
+
+              <View style={{ alignItems: 'flex-end', gap: 2 }}>
+                {row.is_site_admin ? (
+                  <AppText variant="hint" style={{ color: t.brand[600], fontWeight: '600' }}>
+                    Site admin
+                  </AppText>
+                ) : null}
+                {!row.is_active ? (
+                  <AppText variant="hint" style={{ color: t.danger[700] }}>
+                    Deactivated
+                  </AppText>
+                ) : null}
+              </View>
+            </Card>
+          </Pressable>
+        ))}
+
+        {items.length === 0 && !users.isPending ? (
+          <AppText variant="muted">No account matches that.</AppText>
+        ) : null}
+
+        {total > items.length ? (
+          <Button variant="ghost" onPress={() => setLimit((current) => current + PAGE)}>
+            Show more
+          </Button>
+        ) : null}
+      </View>
+
+      {resetting ? (
+        <SetPasswordSheet
+          row={resetting}
+          onClose={() => setResetting(null)}
+          onRun={run}
+        />
+      ) : null}
+    </Sheet>
+  );
+}
+
+/**
+ * Setting a password for somebody locked out.
+ *
+ * The admin types it and passes it on out of band -- there is no email here to
+ * send a reset link through, which is exactly why this exists.
+ */
+function SetPasswordSheet({
+  row,
+  onClose,
+  onRun,
+}: {
+  row: AdminUserRead;
+  onClose: () => void;
+  onRun: (action: () => Promise<void>, fallback: string) => Promise<void>;
+}) {
+  const [password, setPassword] = useState('');
+  const [invalid, setInvalid] = useState<string | null>(null);
+
+  return (
+    <Sheet visible onClose={onClose} title={`Password for ${row.full_name}`}>
+      <View style={{ gap: 12, paddingBottom: 12 }}>
+        {invalid ? <Alert>{invalid}</Alert> : null}
+
+        <Field
+          label="New password"
+          value={password}
+          onChangeText={setPassword}
+          secureTextEntry
+          hint="At least 8 characters. Tell them out of band — nothing is emailed."
+        />
+
+        <Button
+          onPress={() => {
+            if (password.length < 8) {
+              setInvalid('Passwords must be at least 8 characters.');
+              return;
+            }
+            setInvalid(null);
+            void onRun(async () => {
+              await resetPasswordAdminUsersUserIdResetPasswordPost(row.id, {
+                new_password: password,
+              });
+              setPassword('');
+              onClose();
+            }, 'Could not set that password.');
+          }}
+        >
+          Set password
+        </Button>
+      </View>
+    </Sheet>
+  );
+}
diff --git a/src/api/__tests__/live-site-admin.test.ts b/src/api/__tests__/live-site-admin.test.ts
new file mode 100644
index 0000000..e91e4a1
--- /dev/null
+++ b/src/api/__tests__/live-site-admin.test.ts
@@ -0,0 +1,118 @@
+/**
+ * @jest-environment node
+ */
+import {
+  listUsersAdminUsersGet,
+  resetPasswordAdminUsersUserIdResetPasswordPost,
+  updateUserAdminUsersUserIdPatch,
+} from '@/api/generated/endpoints/admin/admin';
+import {
+  loginAuthLoginPost,
+  meAuthMeGet,
+  registerAuthRegisterPost,
+} from '@/api/generated/endpoints/auth/auth';
+import { setInstanceUrl } from '@/api/instance';
+import { persistToken } from '@/auth/session';
+
+/**
+ * The user directory against a real instance.
+ *
+ * The demo account is a site admin, which is what makes this testable at all.
+ */
+const LIVE_URL = process.env.SOFTTRACK_LIVE_URL;
+const describeLive = LIVE_URL ? describe : describe.skip;
+
+const RUN = Date.now().toString(36).slice(-5);
+const SUBJECT_EMAIL = `mob-subject-${RUN}@example.com`;
+
+describeLive('site administration against a live instance', () => {
+  let adminToken: string;
+  let adminId: number;
+  let subjectId: number;
+
+  beforeAll(async () => {
+    await setInstanceUrl(LIVE_URL!);
+    const admin = await loginAuthLoginPost({
+      username: process.env.SOFTTRACK_LIVE_EMAIL ?? 'demo@softtrack.dev',
+      password: process.env.SOFTTRACK_LIVE_PASSWORD ?? 'password123',
+    });
+    adminToken = admin.access_token;
+    adminId = admin.user.id;
+    expect(admin.user.is_site_admin).toBe(true);
+
+    const subject = await registerAuthRegisterPost({
+      email: SUBJECT_EMAIL,
+      password: 'password123',
+      full_name: 'Directory Subject',
+    });
+    subjectId = subject.user.id;
+    await persistToken(adminToken);
+  });
+
+  it('searches the directory', async () => {
+    const page = await listUsersAdminUsersGet({ q: `mob-subject-${RUN}`, limit: 25 });
+    const found = page.items.find((row) => row.id === subjectId);
+    expect(found).toBeDefined();
+    // Every field the row renders.
+    expect(found?.email).toBe(SUBJECT_EMAIL);
+    expect(found?.is_active).toBe(true);
+    expect(found?.is_site_admin).toBe(false);
+    expect(typeof found?.team_count).toBe('number');
+  });
+
+  it('grants and revokes site admin', async () => {
+    const granted = await updateUserAdminUsersUserIdPatch(subjectId, {
+      is_site_admin: true,
+    });
+    expect(granted.is_site_admin).toBe(true);
+
+    const revoked = await updateUserAdminUsersUserIdPatch(subjectId, {
+      is_site_admin: false,
+    });
+    expect(revoked.is_site_admin).toBe(false);
+  });
+
+  it('deactivates and reactivates, and a deactivated account cannot sign in', async () => {
+    await updateUserAdminUsersUserIdPatch(subjectId, { is_active: false });
+
+    // 403 with its own message, which is what login surfaces rather than
+    // "incorrect password".
+    await expect(
+      loginAuthLoginPost({ username: SUBJECT_EMAIL, password: 'password123' }),
+    ).rejects.toMatchObject({ response: { status: 403 } });
+
+    const reactivated = await updateUserAdminUsersUserIdPatch(subjectId, {
+      is_active: true,
+    });
+    expect(reactivated.is_active).toBe(true);
+  });
+
+  it('sets a password for somebody locked out', async () => {
+    // There is no email here to send a reset link through, which is exactly why
+    // this exists.
+    await resetPasswordAdminUsersUserIdResetPasswordPost(subjectId, {
+      new_password: 'brand-new-password',
+    });
+
+    const signedIn = await loginAuthLoginPost({
+      username: SUBJECT_EMAIL,
+      password: 'brand-new-password',
+    });
+    expect(signedIn.user.id).toBe(subjectId);
+    await persistToken(adminToken);
+  });
+
+  it('refuses to let an admin deactivate or demote themselves', async () => {
+    // Both guards the sheet explains up front rather than discovering.
+    await expect(
+      updateUserAdminUsersUserIdPatch(adminId, { is_active: false }),
+    ).rejects.toMatchObject({ response: { status: 400 } });
+
+    await expect(
+      updateUserAdminUsersUserIdPatch(adminId, { is_site_admin: false }),
+    ).rejects.toMatchObject({ response: { status: 400 } });
+
+    // Still a working admin afterwards.
+    expect((await meAuthMeGet()).is_site_admin).toBe(true);
+  });
+});
diff --git a/src/settings/you-screen.tsx b/src/settings/you-screen.tsx
index e0f5768..11cd09d 100644
--- a/src/settings/you-screen.tsx
+++ b/src/settings/you-screen.tsx
@@ -15,6 +15,7 @@ import {
 import { errorDetail } from '@/api/errors';
 import { instanceLabel, setInstanceUrl } from '@/api/instance';
 import { useAuth } from '@/auth/auth-context';
+import { SiteAdminSheet } from '@/admin/site-admin-sheet';
 import { isValidUsername } from '@/settings/username';
 import { useIsMultiPane } from '@/ui/layout';
 import { AppText, Alert, Avatar, Button, Card, Field } from '@/ui/primitives';
@@ -39,7 +40,7 @@ const AVATAR_COLORS = [
   '#22c55e',
 ];
 
-type Panel = 'profile' | 'security' | 'notifications' | 'instance' | null;
+type Panel = 'profile' | 'security' | 'notifications' | 'instance' | 'admin' | null;
 
 export function YouScreen() {
   const t = useTokens();
@@ -78,6 +79,17 @@ export function YouScreen() {
           </Card>
         </View>
 
+        {/* Only for an account that actually has it; there is nothing to
+            discover here that the server would then refuse. */}
+        {user?.is_site_admin ? (
+          <View style={{ gap: 8 }}>
+            <AppText variant="eyebrow">ADMINISTRATION</AppText>
+            <Card>
+              <SettingsRow label="All users" onPress={() => setPanel('admin')} />
+            </Card>
+          </View>
+        ) : null}
+
         <View style={{ gap: 8 }}>
           <AppText variant="eyebrow">APPEARANCE</AppText>
           <ThemePreferenceControl />
@@ -113,6 +125,11 @@ export function YouScreen() {
         visible={panel === 'notifications'}
         onClose={() => setPanel(null)}
       />
+      <SiteAdminSheet
+        visible={panel === 'admin'}
+        onClose={() => setPanel(null)}
+        user={user}
+      />
       <InstancePanel
         visible={panel === 'instance'}
         onClose={() => setPanel(null)}