Preheat your oven to 350°F (175°C).
In a large mixing bowl, combine the shredded chicken, cream of chicken soup, sour cream, celery, and half of the cheddar cheese.
Season the mixture with salt and pepper to taste.
Spread the chicken mixture evenly into a greased 9x13-inch baking dish.
In a separate bowl, mix the crushed Ritz crackers with melted butter.
Sprinkle the remaining cheddar cheese over the chicken mixture.
Top with the Ritz cracker mixture, spreading it evenly.
Bake in the preheated oven for 30 minutes or until bubbly and golden brown.
Let it cool for a few minutes before serving.
Enjoy your delicious Ritz chicken casserole warm!