diff --git a/src/libstore/filetransfer.cc b/src/libstore/filetransfer.cc
index 59fc75ed0..03bf3cda4 100644
--- a/src/libstore/filetransfer.cc
+++ b/src/libstore/filetransfer.cc
@@ -426,6 +426,14 @@ struct curlFileTransfer : public FileTransfer
             curl_easy_setopt(req, CURLOPT_ERRORBUFFER, errbuf);
             errbuf[0] = 0;
 
+            // Set up username/password authentication if provided
+            if (request.usernameAuth) {
+                curl_easy_setopt(req, CURLOPT_USERNAME, request.usernameAuth->username.c_str());
+                if (request.usernameAuth->password) {
+                    curl_easy_setopt(req, CURLOPT_PASSWORD, request.usernameAuth->password->c_str());
+                }
+            }
+
             result.data.clear();
             result.bodySize = 0;
         }
diff --git a/src/libstore/include/nix/store/filetransfer.hh b/src/libstore/include/nix/store/filetransfer.hh
index 2f2d59036..abd9ece5b 100644
--- a/src/libstore/include/nix/store/filetransfer.hh
+++ b/src/libstore/include/nix/store/filetransfer.hh
@@ -77,6 +77,17 @@ extern FileTransferSettings fileTransferSettings;
 
 extern const unsigned int RETRY_TIME_MS_DEFAULT;
 
+/**
+ * Username and optional password for HTTP basic authentication.
+ * These are used with curl's CURLOPT_USERNAME and CURLOPT_PASSWORD options
+ * for various protocols including HTTP, FTP, and others.
+ */
+struct UsernameAuth
+{
+    std::string username;
+    std::optional<std::string> password;
+};
+
 struct FileTransferRequest
 {
     ValidURL uri;
@@ -92,6 +103,11 @@ struct FileTransferRequest
     std::optional<std::string> data;
     std::string mimeType;
     std::function<void(std::string_view data)> dataCallback;
+    /**
+     * Optional username and password for HTTP basic authentication.
+     * When provided, these credentials will be used with curl's CURLOPT_USERNAME/PASSWORD option.
+     */
+    std::optional<UsernameAuth> usernameAuth;
 
     FileTransferRequest(ValidURL uri)
         : uri(std::move(uri))