diff --git a/src/pages/Admin/UserManagement/UserManagement.module.css b/src/pages/Admin/UserManagement/UserManagement.module.css
new file mode 100644
index 0000000..ce8b2eb
--- /dev/null
+++ b/src/pages/Admin/UserManagement/UserManagement.module.css
@@ -0,0 +1,182 @@
+.splitPane {
+  display: grid;
+  grid-template-columns: 52fr 48fr;
+  gap: 1px;
+  background: var(--border-subtle);
+  border: 1px solid var(--border-subtle);
+  border-radius: var(--radius-md);
+  min-height: 500px;
+}
+
+.listPane {
+  background: var(--bg-base);
+  display: flex;
+  flex-direction: column;
+  border-radius: var(--radius-md) 0 0 var(--radius-md);
+}
+
+.detailPane {
+  background: var(--bg-base);
+  overflow-y: auto;
+  padding: 20px;
+  border-radius: 0 var(--radius-md) var(--radius-md) 0;
+}
+
+.listHeader {
+  display: flex;
+  align-items: center;
+  gap: 8px;
+  padding: 12px;
+  border-bottom: 1px solid var(--border-subtle);
+}
+
+.listHeaderSearch {
+  flex: 1;
+}
+
+.entityList {
+  flex: 1;
+  overflow-y: auto;
+}
+
+.entityItem {
+  display: flex;
+  align-items: flex-start;
+  gap: 10px;
+  padding: 10px 12px;
+  cursor: pointer;
+  transition: background 0.1s;
+  border-bottom: 1px solid var(--border-subtle);
+}
+
+.entityItem:hover {
+  background: var(--bg-hover);
+}
+
+.entityItemSelected {
+  background: var(--bg-raised);
+}
+
+.entityInfo {
+  flex: 1;
+  min-width: 0;
+}
+
+.entityName {
+  font-size: 13px;
+  font-weight: 500;
+  color: var(--text-primary);
+  font-family: var(--font-body);
+}
+
+.entityMeta {
+  font-size: 11px;
+  color: var(--text-muted);
+  font-family: var(--font-body);
+  margin-top: 2px;
+}
+
+.entityTags {
+  display: flex;
+  flex-wrap: wrap;
+  gap: 4px;
+  margin-top: 4px;
+}
+
+.detailHeader {
+  display: flex;
+  align-items: center;
+  gap: 12px;
+  margin-bottom: 16px;
+}
+
+.detailHeaderInfo {
+  flex: 1;
+  min-width: 0;
+}
+
+.detailName {
+  font-size: 16px;
+  font-weight: 600;
+  color: var(--text-primary);
+  font-family: var(--font-body);
+}
+
+.detailEmail {
+  font-size: 12px;
+  color: var(--text-muted);
+  font-family: var(--font-body);
+}
+
+.metaGrid {
+  display: grid;
+  grid-template-columns: auto 1fr;
+  gap: 6px 16px;
+  margin-bottom: 16px;
+  font-size: 12px;
+  font-family: var(--font-body);
+}
+
+.metaLabel {
+  color: var(--text-muted);
+  font-weight: 500;
+}
+
+.metaValue {
+  color: var(--text-primary);
+}
+
+.sectionTags {
+  display: flex;
+  flex-wrap: wrap;
+  gap: 6px;
+  margin-top: 8px;
+  margin-bottom: 8px;
+}
+
+.selectWrap {
+  margin-top: 8px;
+  max-width: 240px;
+}
+
+.emptyDetail {
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  height: 100%;
+  color: var(--text-faint);
+  font-size: 13px;
+  font-family: var(--font-body);
+}
+
+.createForm {
+  padding: 12px;
+  border-bottom: 1px solid var(--border-subtle);
+  background: var(--bg-raised);
+  display: flex;
+  flex-direction: column;
+  gap: 8px;
+}
+
+.createFormRow {
+  display: flex;
+  gap: 8px;
+}
+
+.createFormActions {
+  display: flex;
+  gap: 8px;
+  justify-content: flex-end;
+}
+
+.inheritedNote {
+  font-size: 11px;
+  color: var(--text-muted);
+  font-style: italic;
+  font-family: var(--font-body);
+  margin-top: 4px;
+}
+
+.providerBadge {
+  margin-left: 6px;
+}
diff --git a/src/pages/Admin/UserManagement/UserManagement.tsx b/src/pages/Admin/UserManagement/UserManagement.tsx
new file mode 100644
index 0000000..6561b8c
--- /dev/null
+++ b/src/pages/Admin/UserManagement/UserManagement.tsx
@@ -0,0 +1,27 @@
+import { useState } from 'react'
+import { AdminLayout } from '../Admin'
+import { Tabs } from '../../../design-system/composites/Tabs/Tabs'
+import { UsersTab } from './UsersTab'
+import { GroupsTab } from './GroupsTab'
+import { RolesTab } from './RolesTab'
+
+const TABS = [
+  { label: 'Users', value: 'users' },
+  { label: 'Groups', value: 'groups' },
+  { label: 'Roles', value: 'roles' },
+]
+
+export function UserManagement() {
+  const [tab, setTab] = useState('users')
+
+  return (
+    <AdminLayout title="User Management">
+      <Tabs tabs={TABS} active={tab} onChange={setTab} />
+      <div style={{ marginTop: 16 }}>
+        {tab === 'users' && <UsersTab />}
+        {tab === 'groups' && <GroupsTab />}
+        {tab === 'roles' && <RolesTab />}
+      </div>
+    </AdminLayout>
+  )
+}
diff --git a/src/pages/Admin/UserManagement/UsersTab.tsx b/src/pages/Admin/UserManagement/UsersTab.tsx
new file mode 100644
index 0000000..9e54061
--- /dev/null
+++ b/src/pages/Admin/UserManagement/UsersTab.tsx
@@ -0,0 +1,260 @@
+import { useState, useMemo } from 'react'
+import { Avatar } from '../../../design-system/primitives/Avatar/Avatar'
+import { Badge } from '../../../design-system/primitives/Badge/Badge'
+import { Button } from '../../../design-system/primitives/Button/Button'
+import { Input } from '../../../design-system/primitives/Input/Input'
+import { MonoText } from '../../../design-system/primitives/MonoText/MonoText'
+import { SectionHeader } from '../../../design-system/primitives/SectionHeader/SectionHeader'
+import { Tag } from '../../../design-system/primitives/Tag/Tag'
+import { InlineEdit } from '../../../design-system/primitives/InlineEdit/InlineEdit'
+import { MultiSelect } from '../../../design-system/composites/MultiSelect/MultiSelect'
+import { ConfirmDialog } from '../../../design-system/composites/ConfirmDialog/ConfirmDialog'
+import { MOCK_USERS, MOCK_GROUPS, MOCK_ROLES, getEffectiveRoles, type MockUser } from './rbacMocks'
+import styles from './UserManagement.module.css'
+
+export function UsersTab() {
+  const [users, setUsers] = useState(MOCK_USERS)
+  const [search, setSearch] = useState('')
+  const [selectedId, setSelectedId] = useState<string | null>(null)
+  const [creating, setCreating] = useState(false)
+  const [deleteTarget, setDeleteTarget] = useState<MockUser | null>(null)
+
+  // Create form state
+  const [newUsername, setNewUsername] = useState('')
+  const [newDisplay, setNewDisplay] = useState('')
+  const [newEmail, setNewEmail] = useState('')
+  const [newPassword, setNewPassword] = useState('')
+
+  const filtered = useMemo(() => {
+    if (!search) return users
+    const q = search.toLowerCase()
+    return users.filter((u) =>
+      u.displayName.toLowerCase().includes(q) ||
+      u.email.toLowerCase().includes(q) ||
+      u.username.toLowerCase().includes(q)
+    )
+  }, [users, search])
+
+  const selected = users.find((u) => u.id === selectedId) ?? null
+
+  function handleCreate() {
+    if (!newUsername.trim()) return
+    const newUser: MockUser = {
+      id: `usr-${Date.now()}`,
+      username: newUsername.trim(),
+      displayName: newDisplay.trim() || newUsername.trim(),
+      email: newEmail.trim(),
+      provider: 'local',
+      createdAt: new Date().toISOString(),
+      directRoles: [],
+      directGroups: [],
+    }
+    setUsers((prev) => [...prev, newUser])
+    setCreating(false)
+    setNewUsername(''); setNewDisplay(''); setNewEmail(''); setNewPassword('')
+    setSelectedId(newUser.id)
+  }
+
+  function handleDelete() {
+    if (!deleteTarget) return
+    setUsers((prev) => prev.filter((u) => u.id !== deleteTarget.id))
+    if (selectedId === deleteTarget.id) setSelectedId(null)
+    setDeleteTarget(null)
+  }
+
+  function updateUser(id: string, patch: Partial<MockUser>) {
+    setUsers((prev) => prev.map((u) => u.id === id ? { ...u, ...patch } : u))
+  }
+
+  const effectiveRoles = selected ? getEffectiveRoles(selected) : []
+  const availableGroups = MOCK_GROUPS.filter((g) => !selected?.directGroups.includes(g.id))
+    .map((g) => ({ value: g.id, label: g.name }))
+  const availableRoles = MOCK_ROLES.filter((r) => !selected?.directRoles.includes(r.name))
+    .map((r) => ({ value: r.name, label: r.name }))
+
+  function getUserGroupPath(user: MockUser): string {
+    if (user.directGroups.length === 0) return 'no groups'
+    const group = MOCK_GROUPS.find((g) => g.id === user.directGroups[0])
+    if (!group) return 'no groups'
+    const parent = group.parentId ? MOCK_GROUPS.find((g) => g.id === group.parentId) : null
+    return parent ? `${parent.name} > ${group.name}` : group.name
+  }
+
+  return (
+    <>
+      <div className={styles.splitPane}>
+        <div className={styles.listPane}>
+          <div className={styles.listHeader}>
+            <Input
+              placeholder="Search users..."
+              value={search}
+              onChange={(e) => setSearch(e.target.value)}
+              onClear={() => setSearch('')}
+              className={styles.listHeaderSearch}
+            />
+            <Button size="sm" variant="secondary" onClick={() => setCreating(true)}>
+              + Add user
+            </Button>
+          </div>
+
+          {creating && (
+            <div className={styles.createForm}>
+              <div className={styles.createFormRow}>
+                <Input placeholder="Username *" value={newUsername} onChange={(e) => setNewUsername(e.target.value)} />
+                <Input placeholder="Display name" value={newDisplay} onChange={(e) => setNewDisplay(e.target.value)} />
+              </div>
+              <div className={styles.createFormRow}>
+                <Input placeholder="Email" value={newEmail} onChange={(e) => setNewEmail(e.target.value)} />
+                <Input placeholder="Password" type="password" value={newPassword} onChange={(e) => setNewPassword(e.target.value)} />
+              </div>
+              <div className={styles.createFormActions}>
+                <Button size="sm" variant="ghost" onClick={() => setCreating(false)}>Cancel</Button>
+                <Button size="sm" variant="primary" onClick={handleCreate} disabled={!newUsername.trim()}>Create</Button>
+              </div>
+            </div>
+          )}
+
+          <div className={styles.entityList}>
+            {filtered.map((user) => (
+              <div
+                key={user.id}
+                className={`${styles.entityItem} ${selectedId === user.id ? styles.entityItemSelected : ''}`}
+                onClick={() => setSelectedId(user.id)}
+              >
+                <Avatar name={user.displayName} size="sm" />
+                <div className={styles.entityInfo}>
+                  <div className={styles.entityName}>
+                    {user.displayName}
+                    {user.provider !== 'local' && (
+                      <Badge label={user.provider} color="running" variant="outlined" className={styles.providerBadge} />
+                    )}
+                  </div>
+                  <div className={styles.entityMeta}>
+                    {user.email} &middot; {getUserGroupPath(user)}
+                  </div>
+                  <div className={styles.entityTags}>
+                    {user.directRoles.map((r) => <Badge key={r} label={r} color="warning" />)}
+                    {user.directGroups.map((gId) => {
+                      const g = MOCK_GROUPS.find((gr) => gr.id === gId)
+                      return g ? <Badge key={gId} label={g.name} color="success" /> : null
+                    })}
+                  </div>
+                </div>
+              </div>
+            ))}
+          </div>
+        </div>
+
+        <div className={styles.detailPane}>
+          {selected ? (
+            <>
+              <div className={styles.detailHeader}>
+                <Avatar name={selected.displayName} size="lg" />
+                <div className={styles.detailHeaderInfo}>
+                  <div className={styles.detailName}>
+                    <InlineEdit
+                      value={selected.displayName}
+                      onSave={(v) => updateUser(selected.id, { displayName: v })}
+                    />
+                  </div>
+                  <div className={styles.detailEmail}>{selected.email}</div>
+                </div>
+                <Button
+                  size="sm"
+                  variant="danger"
+                  onClick={() => setDeleteTarget(selected)}
+                  disabled={selected.username === 'hendrik'}
+                >
+                  Delete
+                </Button>
+              </div>
+
+              <div className={styles.metaGrid}>
+                <span className={styles.metaLabel}>Status</span>
+                <Badge label="Active" color="success" />
+                <span className={styles.metaLabel}>ID</span>
+                <MonoText size="xs">{selected.id}</MonoText>
+                <span className={styles.metaLabel}>Created</span>
+                <span className={styles.metaValue}>{new Date(selected.createdAt).toLocaleDateString()}</span>
+                <span className={styles.metaLabel}>Provider</span>
+                <span className={styles.metaValue}>{selected.provider}</span>
+              </div>
+
+              <SectionHeader>Group membership (direct only)</SectionHeader>
+              <div className={styles.sectionTags}>
+                {selected.directGroups.map((gId) => {
+                  const g = MOCK_GROUPS.find((gr) => gr.id === gId)
+                  return g ? (
+                    <Tag
+                      key={gId}
+                      label={g.name}
+                      color="success"
+                      onRemove={() => updateUser(selected.id, {
+                        directGroups: selected.directGroups.filter((id) => id !== gId),
+                      })}
+                    />
+                  ) : null
+                })}
+                {selected.directGroups.length === 0 && (
+                  <span className={styles.inheritedNote}>(no groups)</span>
+                )}
+              </div>
+              <div className={styles.selectWrap}>
+                <MultiSelect
+                  options={availableGroups}
+                  value={[]}
+                  onChange={(ids) => updateUser(selected.id, {
+                    directGroups: [...selected.directGroups, ...ids],
+                  })}
+                  placeholder="Add groups..."
+                />
+              </div>
+
+              <SectionHeader>Effective roles (direct + inherited)</SectionHeader>
+              <div className={styles.sectionTags}>
+                {effectiveRoles.map(({ role, source }) => (
+                  <Tag
+                    key={role}
+                    label={source === 'direct' ? role : `${role} ↑ ${source}`}
+                    color="warning"
+                    onRemove={source === 'direct' ? () => updateUser(selected.id, {
+                      directRoles: selected.directRoles.filter((r) => r !== role),
+                    }) : undefined}
+                  />
+                ))}
+                {effectiveRoles.length === 0 && (
+                  <span className={styles.inheritedNote}>(no roles)</span>
+                )}
+              </div>
+              {effectiveRoles.some((r) => r.source !== 'direct') && (
+                <span className={styles.inheritedNote}>
+                  Roles with ↑ are inherited through group membership
+                </span>
+              )}
+              <div className={styles.selectWrap}>
+                <MultiSelect
+                  options={availableRoles}
+                  value={[]}
+                  onChange={(roles) => updateUser(selected.id, {
+                    directRoles: [...selected.directRoles, ...roles],
+                  })}
+                  placeholder="Add roles..."
+                />
+              </div>
+            </>
+          ) : (
+            <div className={styles.emptyDetail}>Select a user to view details</div>
+          )}
+        </div>
+      </div>
+
+      <ConfirmDialog
+        open={deleteTarget !== null}
+        onClose={() => setDeleteTarget(null)}
+        onConfirm={handleDelete}
+        message={`Delete user "${deleteTarget?.username}"? This cannot be undone.`}
+        confirmText={deleteTarget?.username ?? ''}
+      />
+    </>
+  )
+}