Preheat the oven to 425 degrees Fahrenheit. Allow it to fully come to temperature for at least 10 minutes before baking.
Pat the chicken breasts completely dry on both sides with paper towels. Place them in a single layer in a baking dish.
Spoon the marinara sauce evenly over each chicken breast. Sprinkle the shredded mozzarella cheese evenly over the sauce.
Bake uncovered at 425 degrees Fahrenheit for 25 minutes, or until a meat thermometer inserted into the thickest part reads 165 degrees Fahrenheit. The cheese should be melted and beginning to brown in spots.
Remove from the oven and allow the chicken to rest for 3 to 5 minutes before serving so the juices redistribute.