In a large skillet over medium heat, combine the shredded chicken and ranch dressing. Cook for about 5-7 minutes until heated through.
Warm the flour tortillas in a separate pan or microwave for a few seconds until soft.
Assemble the burritos by adding a portion of the chicken mixture, sliced avocado, shredded cheese, lettuce, and diced tomato to each tortilla.
Fold in the sides and roll up the burrito tightly. Repeat with remaining tortillas.
Serve warm with sour cream and cilantro, if desired.
