diff --git a/conf/locale/locale_en-US.ini b/conf/locale/locale_en-US.ini
index 14d39595f..84942da7f 100644
--- a/conf/locale/locale_en-US.ini
+++ b/conf/locale/locale_en-US.ini
@@ -494,6 +494,8 @@ branches.stale_branches = Stale Branches
 branches.all = All Branches
 branches.updated_by = Updated %[1]s by %[2]s
 branches.change_default_branch = Change Default Branch
+branches.default_deletion_not_allowed = Cannot delete the default branch.
+branches.protected_deletion_not_allowed = Cannot delete a protected branch.
 
 editor.new_file = New file
 editor.upload_file = Upload file
diff --git a/internal/route/repo/branch.go b/internal/route/repo/branch.go
index ce4ce66d7..90def186e 100644
--- a/internal/route/repo/branch.go
+++ b/internal/route/repo/branch.go
@@ -118,6 +118,21 @@ func DeleteBranchPost(c *context.Context) {
 	if !c.Repo.GitRepo.HasBranch(branchName) {
 		return
 	}
+	if branchName == c.Repo.Repository.DefaultBranch {
+		c.Flash.Error(c.Tr("repo.branches.default_deletion_not_allowed"))
+		return
+	}
+
+	protectBranch, err := database.GetProtectBranchOfRepoByName(c.Repo.Repository.ID, branchName)
+	if err != nil && !database.IsErrBranchNotExist(err) {
+		log.Error("Failed to get protected branch %q: %v", branchName, err)
+		return
+	}
+	if protectBranch != nil && protectBranch.Protected {
+		c.Flash.Error(c.Tr("repo.branches.protected_deletion_not_allowed"))
+		return
+	}
+
 	if len(commitID) > 0 {
 		branchCommitID, err := c.Repo.GitRepo.BranchCommitID(branchName)
 		if err != nil {