1. Place potatoes in a large pot and cover with water. Bring to a boil over high heat, then reduce heat to medium and cook until tender, about 15-20 minutes. Drain and let cool.
2. In a large mixing bowl, combine mayonnaise, dijon mustard, celery, red onion, and fresh dill. Mix well.
3. Add cooled potatoes to the bowl and gently mix to coat the potatoes with the dressing. Season with salt and black pepper to taste.
4. Refrigerate for at least 1 hour before serving to allow flavors to meld.