Bring a large pot of salted water to a boil.
Add shrimp and cook until pink and opaque, approximately 2 to 3 minutes.
Drain shrimp immediately and transfer to an ice bath to stop the cooking process.
Once cooled, pat the shrimp dry and cut into 1/2-inch pieces.
In a large mixing bowl, whisk together mayonnaise, lemon juice, dill, Old Bay seasoning, salt, and pepper.
Fold in the diced celery and minced red onion.
Add the shrimp to the dressing and toss until evenly coated.
Cover and refrigerate for at least 30 minutes before serving.