diff --git a/.gitea/workflows/deploy.yml b/.gitea/workflows/deploy.yml
index c87c926..2f43fdb 100644
--- a/.gitea/workflows/deploy.yml
+++ b/.gitea/workflows/deploy.yml
@@ -19,6 +19,9 @@ jobs:
           APP_KEY=${{ secrets.APP_KEY }}
           APP_DEBUG=false
           APP_URL=${{ vars.APP_URL }}
+          SHOPIFY_SHOP_DOMAIN=${{ vars.SHOPIFY_SHOP_DOMAIN }}
+          SHOPIFY_ACCESS_TOKEN=${{ secrets.SHOPIFY_ACCESS_TOKEN }}
+          SHOPIFY_WEBHOOK_SECRET=${{ secrets.SHOPIFY_WEBHOOK_SECRET }}
           DB_CONNECTION=mariadb
           DB_HOST=db
           DB_PORT=3306
diff --git a/app/Console/Commands/ShopifyMap.php b/app/Console/Commands/ShopifyMap.php
new file mode 100644
index 0000000..df67223
--- /dev/null
+++ b/app/Console/Commands/ShopifyMap.php
@@ -0,0 +1,57 @@
+<?php
+
+namespace App\Console\Commands;
+
+use App\Models\ProductSize;
+use App\Services\ShopifyService;
+use Illuminate\Console\Command;
+
+class ShopifyMap extends Command
+{
+    protected $signature   = 'shopify:map {--dry-run : Änderungen nur anzeigen, nichts speichern}';
+    protected $description = 'Verknüpft Shopify-Variant-IDs mit lokalen ProductSizes per SKU';
+
+    public function handle(ShopifyService $shopify): int
+    {
+        $dryRun = $this->option('dry-run');
+        $variants = $shopify->getAllVariants();
+
+        $this->info('Shopify-Varianten geladen: ' . count($variants));
+
+        $mapped = 0;
+        $skipped = 0;
+        $noSku = 0;
+
+        foreach ($variants as $variant) {
+            if (empty($variant['sku'])) {
+                $noSku++;
+                continue;
+            }
+
+            $size = ProductSize::where('sku', $variant['sku'])->first();
+
+            if (!$size) {
+                $this->warn("  SKU nicht gefunden: {$variant['sku']} ({$variant['product_title']})");
+                $skipped++;
+                continue;
+            }
+
+            if ($size->shopify_variant_id === $variant['id']) {
+                continue; // already correct
+            }
+
+            if (!$dryRun) {
+                $size->update(['shopify_variant_id' => $variant['id']]);
+            }
+
+            $this->line("  {$variant['sku']} → Variant-ID {$variant['id']}");
+            $mapped++;
+        }
+
+        $this->info("✓ {$mapped} verknüpft" . ($dryRun ? ' (dry-run)' : ''));
+        if ($skipped) $this->warn("⚠ {$skipped} SKUs lokal nicht gefunden");
+        if ($noSku)   $this->warn("⚠ {$noSku} Shopify-Varianten ohne SKU übersprungen");
+
+        return self::SUCCESS;
+    }
+}
diff --git a/app/Console/Commands/ShopifySync.php b/app/Console/Commands/ShopifySync.php
new file mode 100644
index 0000000..cc50003
--- /dev/null
+++ b/app/Console/Commands/ShopifySync.php
@@ -0,0 +1,78 @@
+<?php
+
+namespace App\Console\Commands;
+
+use App\Models\ProductInventory;
+use App\Models\ProductSize;
+use App\Services\ShopifyService;
+use Illuminate\Console\Command;
+use Illuminate\Support\Facades\DB;
+
+class ShopifySync extends Command
+{
+    protected $signature   = 'shopify:sync {--dry-run : Änderungen nur anzeigen, nichts speichern}';
+    protected $description = 'Gleicht lokalen Lagerbestand mit Shopify-Inventar ab';
+
+    public function handle(ShopifyService $shopify): int
+    {
+        $dryRun = $this->option('dry-run');
+        $variants = $shopify->getAllVariants();
+
+        $added   = 0;
+        $removed = 0;
+        $inSync  = 0;
+
+        DB::transaction(function () use ($variants, $dryRun, &$added, &$removed, &$inSync) {
+            foreach ($variants as $variant) {
+                $size = ProductSize::where('shopify_variant_id', $variant['id'])->first();
+
+                if (!$size) {
+                    continue; // not mapped yet — run shopify:map first
+                }
+
+                $shopifyQty = $variant['inventory_quantity'];
+                $localQty   = ProductInventory::where('size_id', $size->id)
+                    ->whereNull('out_at')
+                    ->count();
+
+                if ($localQty === $shopifyQty) {
+                    $inSync++;
+                    continue;
+                }
+
+                $diff = $shopifyQty - $localQty;
+
+                if ($diff > 0) {
+                    // Shopify hat mehr → Einträge hinzufügen
+                    $this->line("  +{$diff} {$variant['product_title']} (SKU {$variant['sku']})");
+                    if (!$dryRun) {
+                        for ($i = 0; $i < $diff; $i++) {
+                            ProductInventory::create([
+                                'product_id' => $size->product_id,
+                                'size_id'    => $size->id,
+                            ]);
+                        }
+                    }
+                    $added += $diff;
+                } else {
+                    // Shopify hat weniger → älteste Einträge als ausgebucht markieren
+                    $excess = abs($diff);
+                    $this->line("  -{$excess} {$variant['product_title']} (SKU {$variant['sku']})");
+                    if (!$dryRun) {
+                        ProductInventory::where('size_id', $size->id)
+                            ->whereNull('out_at')
+                            ->oldest()
+                            ->limit($excess)
+                            ->update(['out_at' => now()]);
+                    }
+                    $removed += $excess;
+                }
+            }
+        });
+
+        $this->info("✓ Sync abgeschlossen" . ($dryRun ? ' (dry-run)' : ''));
+        $this->info("  In Sync: {$inSync} | Hinzugefügt: {$added} | Ausgebucht: {$removed}");
+
+        return self::SUCCESS;
+    }
+}
diff --git a/app/Http/Controllers/ShopifyWebhookController.php b/app/Http/Controllers/ShopifyWebhookController.php
new file mode 100644
index 0000000..04e2dc3
--- /dev/null
+++ b/app/Http/Controllers/ShopifyWebhookController.php
@@ -0,0 +1,63 @@
+<?php
+
+namespace App\Http\Controllers;
+
+use App\Models\ProductInventory;
+use App\Models\ProductSale;
+use App\Models\ProductSize;
+use Illuminate\Http\Request;
+use Illuminate\Http\Response;
+use Illuminate\Support\Facades\DB;
+use Illuminate\Support\Facades\Log;
+
+class ShopifyWebhookController extends Controller
+{
+    public function ordersPaid(Request $request): Response
+    {
+        $order   = $request->json()->all();
+        $orderId = (string) ($order['id'] ?? '');
+
+        // Idempotency: ignore already-processed orders
+        if (ProductSale::where('shopify_order_id', $orderId)->exists()) {
+            return response('', 200);
+        }
+
+        DB::transaction(function () use ($order, $orderId) {
+            foreach ($order['line_items'] ?? [] as $item) {
+                $variantId = (string) ($item['variant_id'] ?? '');
+                $quantity  = (int)   ($item['quantity']   ?? 0);
+
+                if (!$variantId || $quantity <= 0) {
+                    continue;
+                }
+
+                $size = ProductSize::where('shopify_variant_id', $variantId)->first();
+
+                if (!$size) {
+                    Log::warning('Shopify webhook: unbekannte Variant-ID', [
+                        'variant_id' => $variantId,
+                        'order_id'   => $orderId,
+                    ]);
+                    continue;
+                }
+
+                // FIFO: älteste verfügbare Einheiten ausbuchen
+                ProductInventory::where('size_id', $size->id)
+                    ->whereNull('out_at')
+                    ->oldest()
+                    ->limit($quantity)
+                    ->update(['out_at' => now()]);
+
+                ProductSale::create([
+                    'product_id'       => $size->product_id,
+                    'size_id'          => $size->id,
+                    'amount'           => $quantity,
+                    'sold_at'          => now(),
+                    'shopify_order_id' => $orderId,
+                ]);
+            }
+        });
+
+        return response('', 200);
+    }
+}
diff --git a/app/Http/Middleware/VerifyShopifyWebhook.php b/app/Http/Middleware/VerifyShopifyWebhook.php
new file mode 100644
index 0000000..bc2b1ae
--- /dev/null
+++ b/app/Http/Middleware/VerifyShopifyWebhook.php
@@ -0,0 +1,28 @@
+<?php
+
+namespace App\Http\Middleware;
+
+use Closure;
+use Illuminate\Http\Request;
+use Symfony\Component\HttpFoundation\Response;
+
+class VerifyShopifyWebhook
+{
+    public function handle(Request $request, Closure $next): Response
+    {
+        $hmac   = $request->header('X-Shopify-Hmac-Sha256');
+        $secret = config('services.shopify.webhook_secret');
+
+        if (!$hmac || !$secret) {
+            abort(401);
+        }
+
+        $computed = base64_encode(hash_hmac('sha256', $request->getContent(), $secret, true));
+
+        if (!hash_equals($computed, $hmac)) {
+            abort(401);
+        }
+
+        return $next($request);
+    }
+}
diff --git a/app/Models/ProductSale.php b/app/Models/ProductSale.php
index 6f2275b..70331bc 100644
--- a/app/Models/ProductSale.php
+++ b/app/Models/ProductSale.php
@@ -14,6 +14,7 @@ class ProductSale extends Model
         'size_id',
         'amount',
         'sold_at',
+        'shopify_order_id',
     ];
 
     // Beziehungen
diff --git a/app/Models/ProductSize.php b/app/Models/ProductSize.php
index 241ae0e..3428256 100644
--- a/app/Models/ProductSize.php
+++ b/app/Models/ProductSize.php
@@ -9,7 +9,7 @@ class ProductSize extends Model
 {
     use HasFactory;
     protected $table = 'products_sizes';
-    protected $fillable = ['product_id', 'packing_id', 'sku', 'price', 'description'];
+    protected $fillable = ['product_id', 'packing_id', 'sku', 'shopify_variant_id', 'price', 'description'];
 
     public function product() {
         return $this->belongsTo(Product::class);
diff --git a/app/Services/ShopifyService.php b/app/Services/ShopifyService.php
new file mode 100644
index 0000000..f58af45
--- /dev/null
+++ b/app/Services/ShopifyService.php
@@ -0,0 +1,73 @@
+<?php
+
+namespace App\Services;
+
+use Illuminate\Support\Facades\Http;
+use Illuminate\Support\Facades\Log;
+
+class ShopifyService
+{
+    private string $baseUrl;
+    private string $token;
+
+    public function __construct()
+    {
+        $domain = config('services.shopify.domain');
+        $version = config('services.shopify.api_version');
+        $this->baseUrl = "https://{$domain}/admin/api/{$version}";
+        $this->token   = config('services.shopify.access_token');
+    }
+
+    /**
+     * Returns all product variants from Shopify.
+     * Each entry: ['id', 'sku', 'inventory_quantity', 'product_title']
+     */
+    public function getAllVariants(): array
+    {
+        $variants = [];
+        $url = "{$this->baseUrl}/products.json?limit=250&fields=id,title,variants";
+
+        while ($url) {
+            $response = Http::withHeader('X-Shopify-Access-Token', $this->token)->get($url);
+
+            if ($response->failed()) {
+                Log::error('Shopify API error', ['status' => $response->status(), 'body' => $response->body()]);
+                break;
+            }
+
+            foreach ($response->json('products', []) as $product) {
+                foreach ($product['variants'] as $variant) {
+                    $variants[] = [
+                        'id'                => (string) $variant['id'],
+                        'sku'               => $variant['sku'] ?? '',
+                        'inventory_quantity' => (int) ($variant['inventory_quantity'] ?? 0),
+                        'product_title'     => $product['title'],
+                    ];
+                }
+            }
+
+            // Follow Shopify's Link header pagination
+            $url = $this->nextPageUrl($response->header('Link'));
+
+            if ($url) {
+                usleep(500_000); // 0.5s — stay well within 2 req/s limit
+            }
+        }
+
+        return $variants;
+    }
+
+    private function nextPageUrl(?string $linkHeader): ?string
+    {
+        if (!$linkHeader) {
+            return null;
+        }
+
+        // Link: <https://...?page_info=abc>; rel="next"
+        if (preg_match('/<([^>]+)>;\s*rel="next"/', $linkHeader, $m)) {
+            return $m[1];
+        }
+
+        return null;
+    }
+}
diff --git a/config/services.php b/config/services.php
index 27a3617..21ceac2 100644
--- a/config/services.php
+++ b/config/services.php
@@ -35,4 +35,11 @@ return [
         ],
     ],
 
+    'shopify' => [
+        'domain'         => env('SHOPIFY_SHOP_DOMAIN'),
+        'access_token'   => env('SHOPIFY_ACCESS_TOKEN'),
+        'webhook_secret' => env('SHOPIFY_WEBHOOK_SECRET'),
+        'api_version'    => '2024-10',
+    ],
+
 ];
diff --git a/database/migrations/2026_09_11_000001_shopify_variant_ids.php b/database/migrations/2026_09_11_000001_shopify_variant_ids.php
new file mode 100644
index 0000000..24b6746
--- /dev/null
+++ b/database/migrations/2026_09_11_000001_shopify_variant_ids.php
@@ -0,0 +1,33 @@
+<?php
+
+use Illuminate\Database\Migrations\Migration;
+use Illuminate\Database\Schema\Blueprint;
+use Illuminate\Support\Facades\Schema;
+
+return new class extends Migration
+{
+    public function up(): void
+    {
+        Schema::table('products_sizes', function (Blueprint $table) {
+            $table->string('shopify_variant_id')->nullable()->unique()->after('sku');
+        });
+
+        Schema::table('products_sales', function (Blueprint $table) {
+            $table->string('shopify_order_id')->nullable()->after('sold_at');
+            $table->index('shopify_order_id');
+        });
+    }
+
+    public function down(): void
+    {
+        Schema::table('products_sales', function (Blueprint $table) {
+            $table->dropIndex(['shopify_order_id']);
+            $table->dropColumn('shopify_order_id');
+        });
+
+        Schema::table('products_sizes', function (Blueprint $table) {
+            $table->dropUnique(['shopify_variant_id']);
+            $table->dropColumn('shopify_variant_id');
+        });
+    }
+};
diff --git a/routes/api.php b/routes/api.php
index 4b7aa30..364c0cc 100644
--- a/routes/api.php
+++ b/routes/api.php
@@ -1,8 +1,13 @@
 <?php
 
 use App\Http\Controllers\Api\LotController;
+use App\Http\Controllers\ShopifyWebhookController;
+use App\Http\Middleware\VerifyShopifyWebhook;
 use Illuminate\Support\Facades\Route;
 
 Route::get('/lot/{lot_number}', [LotController::class, 'show'])
     ->middleware('throttle:30,1')
     ->name('api.lot');
+
+Route::post('/webhooks/shopify/orders-paid', [ShopifyWebhookController::class, 'ordersPaid'])
+    ->middleware(VerifyShopifyWebhook::class);