Wash the red potatoes thoroughly under cold water.
Place the potatoes in a large pot and cover them with water.
Bring the water to a boil and cook the potatoes for about 15-20 minutes until tender.
Once cooked, drain the potatoes and let them cool slightly.
Cut the potatoes into quarters or halves, depending on their size.
In a large bowl, whisk together mayonnaise, Dijon mustard, and apple cider vinegar.
Add the diced celery and chopped red onion to the bowl.
Gently fold in the potatoes, mixing until well coated.
Season with salt and pepper to taste, and garnish with fresh parsley.
Chill the salad in the refrigerator for at least 30 minutes before serving.