In a large skillet, brown the ground beef over medium heat. Drain off any excess grease.

Stir in the Rotel tomatoes and green chilies, taco seasoning mix, and 1/2 cup water. Bring to a boil, then reduce heat and simmer for 10 minutes, or until the beef is cooked through and the sauce has thickened.

Spoon the beef mixture into the taco shells. Top with your favorite taco toppings and serve.