Bring a large pot of salted water to a boil. Add the diced potatoes and cook until tender but firm, about 10-12 minutes.
Drain the potatoes and let them cool completely.
In a large mixing bowl, combine mayonnaise, mustard, sweet relish, celery, and red onion.
Gently fold in the cooled potatoes and chopped hard-boiled eggs.
Season with salt and pepper to taste.
Cover and refrigerate for at least 2 hours to allow flavors to meld.
Before serving, sprinkle with paprika for garnish, if desired.