In a large skillet over medium heat, cook bacon, flipping once, until crispy, about 8 minutes. Transfer to a paper towel–lined plate. Drain all but 2 tablespoons of bacon fat from the skillet.

Season chicken with salt and pepper. Return skillet to medium-high heat, add chicken and cook until golden and just cooked through, about 6 minutes per side. 

Reduce heat to medium and sprinkle chicken with ranch seasoning and top with mozzarella. Cover the skillet and cook, until cheese is melted and bubbly, about 5 minutes.