diff --git a/src/pkgcheck/checks/profiles.py b/src/pkgcheck/checks/profiles.py
index 625a05d62..a0b8c618f 100644
--- a/src/pkgcheck/checks/profiles.py
+++ b/src/pkgcheck/checks/profiles.py
@@ -498,6 +498,20 @@ def desc(self):
         return f"nonexistent profiles/categories entr{ies}: {categories}"
 
 
+class ArchesOutOfSync(results.ProfilesResult, results.Error):
+    """``profiles/arches.desc`` is out of sync with ``arch.list``."""
+
+    def __init__(self, arches):
+        super().__init__()
+        self.arches = tuple(arches)
+
+    @property
+    def desc(self):
+        es = pluralism(self.arches, plural="es")
+        arches = ", ".join(self.arches)
+        return f"'profiles/arches.desc' is out of sync with 'arch.list', arch{es}: {arches}"
+
+
 def dir_parents(path):
     """Yield all directory path parents excluding the root directory.
 
@@ -533,6 +547,7 @@ class RepoProfilesCheck(RepoCheck):
             ProfileWarning,
             BannedProfileEapi,
             DeprecatedProfileEapi,
+            ArchesOutOfSync,
         ]
     )
 
@@ -614,3 +629,7 @@ def finish(self):
 
         if unused_profile_dirs := available_profile_dirs - seen_profile_dirs:
             yield UnusedProfileDirs(sorted(unused_profile_dirs))
+
+        if arches_desc := frozenset().union(*self.repo.config.arches_desc.values()):
+            if arches_mis_sync := self.repo.known_arches ^ arches_desc:
+                yield ArchesOutOfSync(sorted(arches_mis_sync))
diff --git a/testdata/data/repos/profiledir/RepoProfilesCheck/ArchesOutOfSync/expected.json b/testdata/data/repos/profiledir/RepoProfilesCheck/ArchesOutOfSync/expected.json
new file mode 100644
index 000000000..9e51e311a
--- /dev/null
+++ b/testdata/data/repos/profiledir/RepoProfilesCheck/ArchesOutOfSync/expected.json
@@ -0,0 +1 @@
+{"__class__": "ArchesOutOfSync", "arches": ["unknown_arch"]}
diff --git a/testdata/data/repos/profiledir/RepoProfilesCheck/ArchesOutOfSync/fix.sh b/testdata/data/repos/profiledir/RepoProfilesCheck/ArchesOutOfSync/fix.sh
new file mode 100755
index 000000000..d7c5432ea
--- /dev/null
+++ b/testdata/data/repos/profiledir/RepoProfilesCheck/ArchesOutOfSync/fix.sh
@@ -0,0 +1,2 @@
+#!/bin/bash
+sed -i '/^unknown_arch/d' profiles/arch.list
diff --git a/testdata/repos/profiledir/profiles/arches.desc b/testdata/repos/profiledir/profiles/arches.desc
new file mode 100644
index 000000000..d62663852
--- /dev/null
+++ b/testdata/repos/profiledir/profiles/arches.desc
@@ -0,0 +1,2 @@
+amd64 stable
+x86 testing