diff --git a/apps/mobile/package.json b/apps/mobile/package.json
index b9acd13..f3fc01d 100644
--- a/apps/mobile/package.json
+++ b/apps/mobile/package.json
@@ -9,7 +9,8 @@
     "ios": "expo start --ios",
     "typecheck": "tsc --noEmit",
     "test": "vitest run --passWithNoTests",
-    "i18n:check": "node scripts/i18n-check.mjs"
+    "i18n:check": "node scripts/i18n-check.mjs",
+    "i18n:add-language": "node scripts/i18n-add-language.mjs"
   },
   "dependencies": {
     "@app/analytics": "workspace:*",
diff --git a/apps/mobile/scripts/i18n-add-language.mjs b/apps/mobile/scripts/i18n-add-language.mjs
new file mode 100644
index 0000000..f1fbb3f
--- /dev/null
+++ b/apps/mobile/scripts/i18n-add-language.mjs
@@ -0,0 +1,101 @@
+#!/usr/bin/env node
+/**
+ * i18n:add-language – lägg till ett nytt språk i ett kommando.
+ *
+ *   node scripts/i18n-add-language.mjs <kod> <bcp47-tagg> "<eget namn>"
+ *   ex:  node scripts/i18n-add-language.mjs el el-GR "Ελληνικά"
+ *
+ * Gör ALL plumbing automatiskt:
+ *   1. Skapar src/locales/<kod>/common.json – kopia av svenska (platshållare),
+ *      så appen funkar direkt och paritetsvakten är nöjd från start.
+ *   2. Registrerar språket i src/lib/i18n.ts (import + SUPPORTED_LANGUAGES + resources).
+ *   3. Lägger språkväljar-etiketten profile.language.<kod> = "<eget namn>" i ALLA
+ *      locale-filer (annars faller vakten på saknad nyckel).
+ *
+ * Kvar för dig: översätt värdena i src/locales/<kod>/common.json och kör
+ *   `pnpm --filter @app/mobile i18n:check`  – den listar exakt vad som ev. fattas.
+ *
+ * Endast textinsättning (aldrig omsortering) → minimala diffar på befintliga filer.
+ */
+import { readFileSync, writeFileSync, existsSync, mkdirSync, readdirSync, statSync } from "node:fs";
+import { join } from "node:path";
+
+const ROOT = process.cwd(); // apps/mobile
+const LOC = join(ROOT, "src/locales");
+const I18N = join(ROOT, "src/lib/i18n.ts");
+
+const [code, tag, ...labelParts] = process.argv.slice(2);
+const label = labelParts.join(" ");
+if (!code || !tag || !label) {
+  console.error('Användning: node scripts/i18n-add-language.mjs <kod> <bcp47-tagg> "<eget namn>"');
+  console.error('Exempel:    node scripts/i18n-add-language.mjs el el-GR "Ελληνικά"');
+  process.exit(1);
+}
+if (!/^[a-z]{2,3}$/.test(code)) {
+  console.error(`Ogiltig språkkod "${code}" – 2–3 gemener (t.ex. el, cs, uk).`);
+  process.exit(1);
+}
+if (!/^[a-z]{2,3}-[A-Za-z0-9]{2,4}$/.test(tag)) {
+  console.error(`Ogiltig BCP 47-tagg "${tag}" – t.ex. el-GR, cs-CZ, pt-BR.`);
+  process.exit(1);
+}
+if (existsSync(join(LOC, code, "common.json"))) {
+  console.error(`src/locales/${code}/common.json finns redan – avbryter.`);
+  process.exit(1);
+}
+
+const labelKey = `profile.language.${code}`;
+const labelLine = `  ${JSON.stringify(labelKey)}: ${JSON.stringify(label)},`;
+const ANCHOR = '"profile.language.sv":';
+
+/** Sätt in etikettraden direkt efter profile.language.sv, annars först i objektet. */
+function withLabel(raw) {
+  if (raw.includes(labelKey + '"') || raw.includes(labelKey + "'")) return raw; // finns redan
+  const lines = raw.split("\n");
+  let at = lines.findIndex((l) => l.includes(ANCHOR));
+  if (at === -1) at = lines.findIndex((l) => l.trim().startsWith("{")); // fallback: efter {
+  lines.splice(at + 1, 0, labelLine);
+  return lines.join("\n");
+}
+
+// ---- 1 + 3. Ny fil (kopia av sv + etikett) + etikett i alla befintliga -----
+const svRaw = readFileSync(join(LOC, "sv/common.json"), "utf8");
+mkdirSync(join(LOC, code), { recursive: true });
+writeFileSync(join(LOC, code, "common.json"), withLabel(svRaw));
+
+const existing = readdirSync(LOC).filter((d) => d !== code && statSync(join(LOC, d)).isDirectory());
+for (const lang of existing) {
+  const p = join(LOC, lang, "common.json");
+  writeFileSync(p, withLabel(readFileSync(p, "utf8")));
+}
+
+// ---- 2. Registrera i i18n.ts (import + SUPPORTED_LANGUAGES + resources) -----
+{
+  let lines = readFileSync(I18N, "utf8").split("\n");
+  const importRe = /^import \w+ from "\.\.\/locales\/\w+\/common\.json";$/;
+  let lastImport = -1;
+  lines.forEach((l, i) => importRe.test(l) && (lastImport = i));
+  lines.splice(lastImport + 1, 0, `import ${code} from "../locales/${code}/common.json";`);
+
+  const arrEnd = lines.findIndex((l) => l.trim() === "] as const;");
+  lines.splice(arrEnd, 0, `  { code: "${code}", tag: "${tag}", labelKey: "${labelKey}" },`);
+
+  const resRe = /^\s+\w+: \{ common: \w+ \},$/;
+  let lastRes = -1;
+  lines.forEach((l, i) => resRe.test(l) && (lastRes = i));
+  lines.splice(lastRes + 1, 0, `    ${code}: { common: ${code} },`);
+
+  writeFileSync(I18N, lines.join("\n"));
+}
+
+const keyCount = svRaw.split("\n").filter((l) => l.includes('": ')).length;
+console.log(`\n✓ La till "${code}" (${tag}, "${label}").`);
+console.log(
+  `  • src/locales/${code}/common.json skapad (~${keyCount} nycklar, svenska platshållare)`,
+);
+console.log(`  • registrerad i src/lib/i18n.ts (import + SUPPORTED_LANGUAGES + resources)`);
+console.log(`  • ${labelKey} = "${label}" i alla locale-filer`);
+console.log(`\nNästa steg:`);
+console.log(`  1. Översätt värdena i src/locales/${code}/common.json`);
+console.log(`  2. pnpm --filter @app/mobile i18n:check`);
+console.log(`  3. pnpm --filter @app/mobile typecheck`);