diff --git a/highscore/scores/api/pagination.py b/highscore/scores/api/pagination.py
index 9d54645..4bfe719 100644
--- a/highscore/scores/api/pagination.py
+++ b/highscore/scores/api/pagination.py
@@ -1,7 +1,7 @@
-from app.api_base import BaseSchema
-
 from ninja.pagination import PageNumberPagination as _PageNumberPagination
 
+from app.api_base import BaseSchema
+
 
 class PageNumberPagination(_PageNumberPagination):
     class Input(_PageNumberPagination.Input, BaseSchema):
diff --git a/highscore/scores/api/views.py b/highscore/scores/api/views.py
index 3cd7ec4..7b0840a 100644
--- a/highscore/scores/api/views.py
+++ b/highscore/scores/api/views.py
@@ -8,8 +8,8 @@ from ninja.pagination import paginate
 from app.api_base import CamelCaseRouter
 from scores.models import Score, Version
 
-from .schemas import ScoreIn, ScoreOut
 from .pagination import PageNumberPagination
+from .schemas import ScoreIn, ScoreOut
 
 router = CamelCaseRouter()
 
@@ -42,4 +42,4 @@ def list_scores(
     x_game_version: GameVersionHeader = None,
 ) -> QuerySet[Score]:
     version = resolve_version(x_game_version)
-    return Score.objects.filter(version=version)
+    return Score.objects.filter(version=version).best_per_username().with_rank()
diff --git a/highscore/scores/models.py b/highscore/scores/models.py
index 42d27e6..f23deaa 100644
--- a/highscore/scores/models.py
+++ b/highscore/scores/models.py
@@ -1,7 +1,7 @@
 from django.db import models
 from django.db.models import F
 from django.db.models.expressions import Window
-from django.db.models.functions import Rank
+from django.db.models.functions import Lower, Rank, RowNumber
 
 
 class Version(models.Model):
@@ -12,19 +12,37 @@ class Version(models.Model):
         return self.name
 
 
-class ScoreManager(models.Manager):
-    def get_queryset(self) -> models.QuerySet["Score"]:
-        return (
-            super()
-            .get_queryset()
-            .select_related("version")
-            .annotate(
-                rank=Window(
-                    expression=Rank(),
-                    order_by=F("points").desc(),
+class ScoreQuerySet(models.QuerySet):
+    def best_per_username(self) -> "ScoreQuerySet":
+        """Keep only each user's highest score, matching usernames case-insensitively.
+
+        Lower scores are excluded from the result but remain in the database.
+        """
+        best_ids = (
+            self.alias(
+                _row=Window(
+                    expression=RowNumber(),
+                    partition_by=Lower("username"),
+                    order_by=[F("points").desc(), F("created_at").asc()],
                 )
             )
+            .filter(_row=1)
+            .values_list("pk", flat=True)
         )
+        return self.filter(pk__in=best_ids)
+
+    def with_rank(self) -> "ScoreQuerySet":
+        return self.annotate(
+            rank=Window(
+                expression=Rank(),
+                order_by=F("points").desc(),
+            )
+        )
+
+
+class ScoreManager(models.Manager.from_queryset(ScoreQuerySet)):
+    def get_queryset(self) -> ScoreQuerySet:
+        return super().get_queryset().select_related("version")
 
 
 class Score(models.Model):
diff --git a/highscore/scores/tests.py b/highscore/scores/tests.py
index a39b155..03438e7 100644
--- a/highscore/scores/tests.py
+++ b/highscore/scores/tests.py
@@ -1 +1,38 @@
-# Create your tests here.
+from django.test import TestCase
+
+from scores.models import Score, Version
+
+
+class BestPerUsernameTests(TestCase):
+    @classmethod
+    def setUpTestData(cls) -> None:
+        cls.version = Version.objects.create(name="default")
+        cls.other = Version.objects.create(name="other")
+
+        Score.objects.create(username="legrems", points=120, version=cls.version)
+        Score.objects.create(username="Legrems", points=119, version=cls.version)
+        Score.objects.create(username="legrems", points=50, version=cls.version)
+        Score.objects.create(username="alice", points=200, version=cls.version)
+        # Same user, different version: must not collide across versions.
+        Score.objects.create(username="legrems", points=999, version=cls.other)
+
+    def _best(self) -> list[Score]:
+        return list(Score.objects.filter(version=self.version).best_per_username().with_rank())
+
+    def test_keeps_only_highest_per_case_insensitive_username(self) -> None:
+        results = self._best()
+
+        self.assertEqual(len(results), 2)
+        by_name = {s.username.lower(): s for s in results}
+        self.assertEqual(by_name["legrems"].points, 120)
+        self.assertEqual(by_name["alice"].points, 200)
+
+    def test_ranks_recomputed_over_deduplicated_set(self) -> None:
+        results = self._best()
+        ranks = {s.username.lower(): s.rank for s in results}
+
+        self.assertEqual(ranks["alice"], 1)
+        self.assertEqual(ranks["legrems"], 2)
+
+    def test_lower_scores_remain_in_db(self) -> None:
+        self.assertEqual(Score.objects.filter(version=self.version).count(), 4)