diff --git a/models/quota/default.go b/models/quota/default.go
new file mode 100644
index 0000000000..6b553d6f71
--- /dev/null
+++ b/models/quota/default.go
@@ -0,0 +1,25 @@
+// Copyright 2024 The Forgejo Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package quota
+
+import (
+	"code.gitea.io/gitea/modules/setting"
+)
+
+func EvaluateDefault(used Used, forSubject LimitSubject) bool {
+	groups := GroupList{
+		&Group{
+			Name: "builtin-default-group",
+			Rules: []Rule{
+				{
+					Name:     "builtin-default-rule",
+					Limit:    setting.Quota.Default.Total,
+					Subjects: LimitSubjects{LimitSubjectSizeAll},
+				},
+			},
+		},
+	}
+
+	return groups.Evaluate(used, forSubject)
+}
diff --git a/models/quota/group.go b/models/quota/group.go
index 045a98ec21..0acb5b255e 100644
--- a/models/quota/group.go
+++ b/models/quota/group.go
@@ -230,9 +230,9 @@ func (g *Group) Evaluate(used Used, forSubject LimitSubject) (bool, bool) {
 }
 
 func (gl *GroupList) Evaluate(used Used, forSubject LimitSubject) bool {
-	// If there are no groups, default to success:
+	// If there are no groups, use the configured defaults:
 	if gl == nil || len(*gl) == 0 {
-		return true
+		return EvaluateDefault(used, forSubject)
 	}
 
 	for _, group := range *gl {
diff --git a/modules/setting/quota.go b/modules/setting/quota.go
index 6dfadb59f6..05e14baa9c 100644
--- a/modules/setting/quota.go
+++ b/modules/setting/quota.go
@@ -7,9 +7,18 @@ package setting
 var Quota = struct {
 	Enabled       bool     `ini:"ENABLED"`
 	DefaultGroups []string `ini:"DEFAULT_GROUPS"`
+
+	Default struct {
+		Total int64
+	} `ini:"quota.default"`
 }{
 	Enabled:       false,
 	DefaultGroups: []string{},
+	Default: struct {
+		Total int64
+	}{
+		Total: -1,
+	},
 }
 
 func loadQuotaFrom(rootCfg ConfigProvider) {
diff --git a/tests/integration/quota_use_test.go b/tests/integration/quota_use_test.go
index 06f23c9c23..39c5c1ae5c 100644
--- a/tests/integration/quota_use_test.go
+++ b/tests/integration/quota_use_test.go
@@ -548,6 +548,42 @@ func TestGitQuotaEnforcement(t *testing.T) {
 	})
 }
 
+func TestQuotaConfigDefault(t *testing.T) {
+	onGiteaRun(t, func(t *testing.T, u *url.URL) {
+		env := createQuotaWebEnv(t)
+		defer env.Cleanup()
+
+		t.Run("with config-based default", func(t *testing.T) {
+			defer tests.PrintCurrentTest(t)()
+			defer test.MockVariableValue(&setting.Quota.Default.Total, 0)()
+
+			env.As(t, env.Users.Ungrouped).
+				With(Context{
+					Payload: &Payload{
+						"uid":       env.Users.Ungrouped.ID().AsString(),
+						"repo_name": "quota-config-default",
+					},
+				}).
+				PostToPage("/repo/create").
+				ExpectStatus(http.StatusRequestEntityTooLarge)
+		})
+
+		t.Run("without config-based default", func(t *testing.T) {
+			defer tests.PrintCurrentTest(t)()
+
+			env.As(t, env.Users.Ungrouped).
+				With(Context{
+					Payload: &Payload{
+						"uid":       env.Users.Ungrouped.ID().AsString(),
+						"repo_name": "quota-config-default",
+					},
+				}).
+				PostToPage("/repo/create").
+				ExpectStatus(http.StatusSeeOther)
+		})
+	})
+}
+
 /**********************
  * Here be dragons!   *
  *                    *
@@ -568,6 +604,7 @@ type quotaWebEnv struct {
 type quotaWebEnvUsers struct {
 	Limited     quotaWebEnvUser
 	Contributor quotaWebEnvUser
+	Ungrouped   quotaWebEnvUser
 }
 
 type quotaWebEnvOrgs struct {
@@ -1005,8 +1042,7 @@ func createQuotaWebEnv(t *testing.T) *quotaWebEnv {
 
 	// *** helpers ***
 
-	// Create a user, its quota group & rule
-	makeUser := func(t *testing.T, limit int64) quotaWebEnvUser {
+	makeUngroupedUser := func(t *testing.T) quotaWebEnvUser {
 		t.Helper()
 
 		user := quotaWebEnvUser{}
@@ -1021,6 +1057,16 @@ func createQuotaWebEnv(t *testing.T) *quotaWebEnv {
 		repo, _, _ := tests.CreateDeclarativeRepoWithOptions(t, user.User, tests.DeclarativeRepoOptions{})
 		user.Repo = repo
 
+		return user
+	}
+
+	// Create a user, its quota group & rule
+	makeUser := func(t *testing.T, limit int64) quotaWebEnvUser {
+		t.Helper()
+
+		user := makeUngroupedUser(t)
+		userName := user.User.Name
+
 		// Create a quota group for them
 		group, err := quota_model.CreateGroup(db.DefaultContext, userName)
 		require.NoError(t, err)
@@ -1095,5 +1141,7 @@ func createQuotaWebEnv(t *testing.T) *quotaWebEnv {
 	env.Orgs.Limited = makeOrg(t, env.Users.Limited.User, int64(0))
 	env.Orgs.Unlimited = makeOrg(t, env.Users.Limited.User, int64(-1))
 
+	env.Users.Ungrouped = makeUngroupedUser(t)
+
 	return &env
 }