diff --git a/gerbil-manager-web/src/App.tsx b/gerbil-manager-web/src/App.tsx
index 21094ea..a6b0ecf 100644
--- a/gerbil-manager-web/src/App.tsx
+++ b/gerbil-manager-web/src/App.tsx
@@ -2,6 +2,8 @@ import { BrowserRouter, Route, Routes } from 'react-router-dom'
 import AppShell from './components/AppShell'
 import BreedersPage from './pages/BreedersPage'
 import GerbilsPage from './pages/GerbilsPage'
+import GerbilDetailPage from './pages/GerbilDetailPage'
+import GerbilFormPage from './pages/GerbilFormPage'
 import HomePage from './pages/HomePage'
 import LittersPage from './pages/LittersPage'
 import NotFoundPage from './pages/NotFoundPage'
@@ -12,7 +14,12 @@ export default function App() {
       <Routes>
         <Route element={<AppShell />}>
           <Route index element={<HomePage />} />
-          <Route path="rennmaeuse" element={<GerbilsPage />} />
+          <Route path="rennmaeuse">
+            <Route index element={<GerbilsPage />} />
+            <Route path="neu" element={<GerbilFormPage />} />
+            <Route path=":id" element={<GerbilDetailPage />} />
+            <Route path=":id/bearbeiten" element={<GerbilFormPage />} />
+          </Route>
           <Route path="wuerfe" element={<LittersPage />} />
           <Route path="zuechter" element={<BreedersPage />} />
           <Route path="*" element={<NotFoundPage />} />
diff --git a/gerbil-manager-web/src/index.css b/gerbil-manager-web/src/index.css
index 77ed128..5d00c61 100644
--- a/gerbil-manager-web/src/index.css
+++ b/gerbil-manager-web/src/index.css
@@ -431,3 +431,29 @@ textarea {
   white-space: nowrap;
   border: 0;
 }
+
+/* ── Form ────────────────────────────────────────────────────── */
+
+.form {
+  display: flex;
+  flex-direction: column;
+  gap: 1rem;
+  max-width: 32rem;
+  margin-top: 1rem;
+}
+
+.form .field > span {
+  font-size: 0.85rem;
+  color: var(--color-text-muted);
+}
+
+.error-text {
+  color: #b54a4a;
+  font-size: 0.8rem;
+}
+
+.form-actions {
+  display: flex;
+  gap: 0.75rem;
+  margin-top: 0.5rem;
+}
diff --git a/gerbil-manager-web/src/pages/GerbilFormPage.tsx b/gerbil-manager-web/src/pages/GerbilFormPage.tsx
new file mode 100644
index 0000000..7356c86
--- /dev/null
+++ b/gerbil-manager-web/src/pages/GerbilFormPage.tsx
@@ -0,0 +1,344 @@
+import { useState, type FormEvent } from 'react'
+import { Link, useNavigate, useParams } from 'react-router-dom'
+import { de } from '../strings/de'
+import { createGerbil, getGerbil, updateGerbil } from '../api/gerbils'
+import { listColorVarieties, listContacts, listEnclosures, listLitters } from '../api/lookups'
+import { GENDERS, GERBIL_STATUSES, type CreateGerbil, type Gender, type GerbilStatus } from '../api/types'
+import { useApi, useMutation } from '../hooks/useApi'
+import { genderLabel, statusLabel } from '../format/labels'
+import { fromDisplayString } from '../genetics'
+
+interface FormState {
+  name: string
+  gender: Gender | ''
+  status: GerbilStatus
+  dateOfBirth: string
+  dateOfDeath: string
+  causeOfDeath: string
+  goHomeDate: string
+  colorVarietyId: string
+  enclosureId: string
+  litterId: string
+  originContactId: string
+  receiverContactId: string
+  genotype: string
+  notes: string
+}
+
+const EMPTY: FormState = {
+  name: '',
+  gender: '',
+  status: 'Active',
+  dateOfBirth: '',
+  dateOfDeath: '',
+  causeOfDeath: '',
+  goHomeDate: '',
+  colorVarietyId: '',
+  enclosureId: '',
+  litterId: '',
+  originContactId: '',
+  receiverContactId: '',
+  genotype: '',
+  notes: '',
+}
+
+function formFromGerbil(g: {
+  name: string
+  gender: Gender
+  status: GerbilStatus
+  dateOfBirth: string | null
+  dateOfDeath: string | null
+  causeOfDeath: string | null
+  goHomeDate: string | null
+  colorVarietyId: string | null
+  enclosureId: string | null
+  litterId: string | null
+  originContactId: string | null
+  receiverContactId: string | null
+  genotype: string | null
+  notes: string | null
+}): FormState {
+  return {
+    name: g.name,
+    gender: g.gender,
+    status: g.status,
+    dateOfBirth: g.dateOfBirth ?? '',
+    dateOfDeath: g.dateOfDeath ?? '',
+    causeOfDeath: g.causeOfDeath ?? '',
+    goHomeDate: g.goHomeDate ?? '',
+    colorVarietyId: g.colorVarietyId ?? '',
+    enclosureId: g.enclosureId ?? '',
+    litterId: g.litterId ?? '',
+    originContactId: g.originContactId ?? '',
+    receiverContactId: g.receiverContactId ?? '',
+    genotype: g.genotype ?? '',
+    notes: g.notes ?? '',
+  }
+}
+
+/** "" -> null, else the value. */
+const nn = (s: string): string | null => (s.trim() === '' ? null : s)
+
+function isGenotypeValid(genotype: string): boolean {
+  if (genotype.trim() === '') return true
+  try {
+    fromDisplayString(genotype)
+    return true
+  } catch {
+    return false
+  }
+}
+
+export default function GerbilFormPage() {
+  const t = de.pages.gerbils
+  const navigate = useNavigate()
+  const { id } = useParams()
+  const isEdit = Boolean(id)
+
+  const [form, setForm] = useState<FormState>(EMPTY)
+  const [errors, setErrors] = useState<Partial<Record<keyof FormState, string>>>({})
+  const [initializedFor, setInitializedFor] = useState<string | null>(null)
+
+  const existing = useApi(() => (id ? getGerbil(id) : Promise.resolve(null)), [id])
+  const colorVarieties = useApi(() => listColorVarieties(), [])
+  const enclosures = useApi(() => listEnclosures(), [])
+  const contacts = useApi(() => listContacts(), [])
+  const litters = useApi(() => listLitters(), [])
+
+  // Prefill from the loaded gerbil once (edit mode). React's "adjust state
+  // during render" pattern — runs without an effect and re-renders immediately.
+  if (existing.data && initializedFor !== existing.data.id) {
+    setInitializedFor(existing.data.id)
+    setForm(formFromGerbil(existing.data))
+  }
+
+  const set = <K extends keyof FormState>(key: K, value: FormState[K]) =>
+    setForm((f) => ({ ...f, [key]: value }))
+
+  const mutation = useMutation((body: CreateGerbil) =>
+    isEdit && id ? updateGerbil(id, body) : createGerbil(body),
+  )
+
+  function validate(): boolean {
+    const next: Partial<Record<keyof FormState, string>> = {}
+    if (form.name.trim() === '') next.name = t.validation.nameRequired
+    if (form.gender === '') next.gender = t.validation.genderRequired
+    if (!isGenotypeValid(form.genotype)) next.genotype = t.validation.genotypeInvalid
+    if (form.dateOfBirth && form.dateOfDeath && form.dateOfDeath < form.dateOfBirth) {
+      next.dateOfDeath = t.validation.dateOfDeathBeforeBirth
+    }
+    setErrors(next)
+    return Object.keys(next).length === 0
+  }
+
+  async function onSubmit(e: FormEvent) {
+    e.preventDefault()
+    if (!validate()) return
+    const body: CreateGerbil = {
+      name: form.name.trim(),
+      gender: form.gender as Gender,
+      status: form.status,
+      dateOfBirth: nn(form.dateOfBirth),
+      dateOfDeath: nn(form.dateOfDeath),
+      causeOfDeath: nn(form.causeOfDeath),
+      goHomeDate: nn(form.goHomeDate),
+      colorVarietyId: nn(form.colorVarietyId),
+      enclosureId: nn(form.enclosureId),
+      litterId: nn(form.litterId),
+      originContactId: nn(form.originContactId),
+      receiverContactId: nn(form.receiverContactId),
+      genotype: nn(form.genotype),
+      notes: nn(form.notes),
+    }
+    const saved = await mutation.run(body)
+    navigate(`/rennmaeuse/${saved.id}`)
+  }
+
+  if (isEdit && existing.loading) return <p className="muted">{de.common.loading}</p>
+
+  return (
+    <section className="page">
+      <h2>{isEdit ? t.form.editTitle : t.form.createTitle}</h2>
+
+      <form className="form" onSubmit={onSubmit} noValidate>
+        <label className="field">
+          <span>{t.fields.name} *</span>
+          <input
+            className="input"
+            value={form.name}
+            onChange={(e) => set('name', e.target.value)}
+            aria-invalid={Boolean(errors.name)}
+          />
+          {errors.name && <small className="error-text">{errors.name}</small>}
+        </label>
+
+        <label className="field">
+          <span>{t.fields.gender} *</span>
+          <select
+            value={form.gender}
+            onChange={(e) => set('gender', e.target.value as Gender | '')}
+            aria-invalid={Boolean(errors.gender)}
+          >
+            <option value="">{t.form.none}</option>
+            {GENDERS.map((g) => (
+              <option key={g} value={g}>
+                {genderLabel(g)}
+              </option>
+            ))}
+          </select>
+          {errors.gender && <small className="error-text">{errors.gender}</small>}
+        </label>
+
+        <label className="field">
+          <span>{t.fields.status}</span>
+          <select value={form.status} onChange={(e) => set('status', e.target.value as GerbilStatus)}>
+            {GERBIL_STATUSES.map((s) => (
+              <option key={s} value={s}>
+                {statusLabel(s)}
+              </option>
+            ))}
+          </select>
+        </label>
+
+        <label className="field">
+          <span>{t.fields.dateOfBirth}</span>
+          <input
+            type="date"
+            className="input"
+            value={form.dateOfBirth}
+            onChange={(e) => set('dateOfBirth', e.target.value)}
+          />
+        </label>
+
+        {form.status === 'Deceased' && (
+          <>
+            <label className="field">
+              <span>{t.fields.dateOfDeath}</span>
+              <input
+                type="date"
+                className="input"
+                value={form.dateOfDeath}
+                onChange={(e) => set('dateOfDeath', e.target.value)}
+                aria-invalid={Boolean(errors.dateOfDeath)}
+              />
+              {errors.dateOfDeath && <small className="error-text">{errors.dateOfDeath}</small>}
+            </label>
+            <label className="field">
+              <span>{t.fields.causeOfDeath}</span>
+              <input
+                className="input"
+                value={form.causeOfDeath}
+                onChange={(e) => set('causeOfDeath', e.target.value)}
+              />
+            </label>
+          </>
+        )}
+
+        {form.status === 'GivenAway' && (
+          <label className="field">
+            <span>{t.fields.goHomeDate}</span>
+            <input
+              type="date"
+              className="input"
+              value={form.goHomeDate}
+              onChange={(e) => set('goHomeDate', e.target.value)}
+            />
+          </label>
+        )}
+
+        <label className="field">
+          <span>{t.fields.colorVariety}</span>
+          <select value={form.colorVarietyId} onChange={(e) => set('colorVarietyId', e.target.value)}>
+            <option value="">{t.form.none}</option>
+            {(colorVarieties.data ?? []).map((cv) => (
+              <option key={cv.id} value={cv.id}>
+                {cv.name}
+              </option>
+            ))}
+          </select>
+        </label>
+
+        <label className="field">
+          <span>{t.fields.enclosure}</span>
+          <select value={form.enclosureId} onChange={(e) => set('enclosureId', e.target.value)}>
+            <option value="">{t.form.none}</option>
+            {(enclosures.data ?? []).map((en) => (
+              <option key={en.id} value={en.id}>
+                {en.name}
+              </option>
+            ))}
+          </select>
+        </label>
+
+        <label className="field">
+          <span>{t.fields.litter}</span>
+          <select value={form.litterId} onChange={(e) => set('litterId', e.target.value)}>
+            <option value="">{t.form.none}</option>
+            {(litters.data ?? []).map((l) => (
+              <option key={l.id} value={l.id}>
+                {l.name}
+              </option>
+            ))}
+          </select>
+        </label>
+
+        <label className="field">
+          <span>{t.fields.origin}</span>
+          <select value={form.originContactId} onChange={(e) => set('originContactId', e.target.value)}>
+            <option value="">{t.form.none}</option>
+            {(contacts.data ?? []).map((c) => (
+              <option key={c.id} value={c.id}>
+                {c.name}
+              </option>
+            ))}
+          </select>
+        </label>
+
+        <label className="field">
+          <span>{t.fields.receiver}</span>
+          <select
+            value={form.receiverContactId}
+            onChange={(e) => set('receiverContactId', e.target.value)}
+          >
+            <option value="">{t.form.none}</option>
+            {(contacts.data ?? []).map((c) => (
+              <option key={c.id} value={c.id}>
+                {c.name}
+              </option>
+            ))}
+          </select>
+        </label>
+
+        <label className="field">
+          <span>{t.fields.genotype}</span>
+          <input
+            className="input"
+            value={form.genotype}
+            placeholder="Aa CC Dd EE GG Pp Spsp rere"
+            onChange={(e) => set('genotype', e.target.value)}
+            aria-invalid={Boolean(errors.genotype)}
+          />
+          <small className={errors.genotype ? 'error-text' : 'muted'}>
+            {errors.genotype ?? t.form.genotypeHint}
+          </small>
+        </label>
+
+        <label className="field">
+          <span>{t.fields.notes}</span>
+          <textarea value={form.notes} onChange={(e) => set('notes', e.target.value)} />
+        </label>
+
+        {mutation.error && <div className="alert alert--error">{mutation.error}</div>}
+
+        <div className="form-actions">
+          <button type="submit" className="btn btn--primary" disabled={mutation.pending}>
+            {mutation.pending ? t.form.saving : t.form.save}
+          </button>
+          <Link to={isEdit && id ? `/rennmaeuse/${id}` : '/rennmaeuse'} className="btn">
+            {t.form.cancel}
+          </Link>
+        </div>
+      </form>
+    </section>
+  )
+}