diff --git a/lisp/progmodes/project.el b/lisp/progmodes/project.el
index 57a961c260..8eee0c7d27 100644
--- a/lisp/progmodes/project.el
+++ b/lisp/progmodes/project.el
@@ -165,7 +165,7 @@ project
   :version "28.1"
   :group 'tools)
 
-(defvar project-find-functions (list #'project-try-vc)
+(defvar project-find-functions (list #'project-try-vc #'project-try-fallback)
   "Special hook to find the project containing a given directory.
 Each functions on this hook is called in turn with one
 argument, the directory in which to look, and should return
@@ -662,6 +662,27 @@ project-buffers
         (push buf bufs)))
     (nreverse bufs)))
 
+(defcustom project-fallback-markers '(".dir-locals.el")
+  "List of file name to use as fallback project root markers.
+
+Each entry should be a relative file name (no directory part).
+
+The fallback project backend detects a project as a directory
+containing one of these files."
+  :type 'list)
+
+(defun project-try-fallback (dir)
+  (let ((root (locate-dominating-file dir #'project-fallback--root-p)))
+    (and root (cons 'fallback root))))
+
+(defun project-fallback--root-p (dir)
+  (let ((default-directory dir))
+    (seq-some (lambda (marker) (file-exists-p marker))
+              project-fallback-markers)))
+
+(cl-defmethod project-root ((project (head fallback)))
+  (cdr project))
+
 
 ;;; Project commands