diff --git a/api/admin.py b/api/admin.py
index 611bdba0..100dcd69 100644
--- a/api/admin.py
+++ b/api/admin.py
@@ -17,6 +17,15 @@ class ApiClientAdmin(admin.ModelAdmin):
         "owner__nick_name",
     )
     autocomplete_fields = ("owner", "groups", "client_permissions")
+    readonly_fields = ("hmac_key",)
+    actions = ("reset_hmac_key",)
+
+    @admin.action(permissions=["change"], description=_("Reset HMAC key"))
+    def reset_hmac_key(self, _request: HttpRequest, queryset: QuerySet[ApiClient]):
+        objs = list(queryset)
+        for obj in objs:
+            obj.reset_hmac(commit=False)
+        ApiClient.objects.bulk_update(objs, fields=["hmac_key"])
 
 
 @admin.register(ApiKey)
diff --git a/api/migrations/0002_apiclient_hmac_key.py b/api/migrations/0002_apiclient_hmac_key.py
new file mode 100644
index 00000000..d0b3fad4
--- /dev/null
+++ b/api/migrations/0002_apiclient_hmac_key.py
@@ -0,0 +1,19 @@
+# Generated by Django 5.2.3 on 2025-10-26 10:15
+
+from django.db import migrations, models
+
+import api.models
+
+
+class Migration(migrations.Migration):
+    dependencies = [("api", "0001_initial")]
+
+    operations = [
+        migrations.AddField(
+            model_name="apiclient",
+            name="hmac_key",
+            field=models.CharField(
+                default=api.models.get_hmac_key, max_length=128, verbose_name="HMAC Key"
+            ),
+        ),
+    ]
diff --git a/api/models.py b/api/models.py
index 4c802b55..c0d9c291 100644
--- a/api/models.py
+++ b/api/models.py
@@ -1,3 +1,4 @@
+import secrets
 from typing import Iterable
 
 from django.contrib.auth.models import Permission
@@ -10,6 +11,10 @@ from django.utils.translation import pgettext_lazy
 from core.models import Group, User
 
 
+def get_hmac_key():
+    return secrets.token_hex(64)
+
+
 class ApiClient(models.Model):
     name = models.CharField(_("name"), max_length=64)
     owner = models.ForeignKey(
@@ -28,6 +33,7 @@ class ApiClient(models.Model):
         help_text=_("Specific permissions for this api client."),
         related_name="clients",
     )
+    hmac_key = models.CharField(_("HMAC Key"), max_length=128, default=get_hmac_key)
     created_at = models.DateTimeField(auto_now_add=True)
     updated_at = models.DateTimeField(auto_now=True)
 
@@ -59,6 +65,13 @@ class ApiClient(models.Model):
             raise ValueError("perm_list must be an iterable of permissions.")
         return all(self.has_perm(perm) for perm in perm_list)
 
+    def reset_hmac(self, *, commit: bool = True) -> str:
+        """Reset and return the HMAC key for this client."""
+        self.hmac_key = get_hmac_key()
+        if commit:
+            self.save()
+        return self.hmac_key
+
 
 class ApiKey(models.Model):
     PREFIX_LENGTH = 5