I believe there are a few reindeer that start with the letter "D." I believe the most famous reindeer that begins with "D" is Donner, who was one of Santa's original reindeer. He was known for his loyalty and his strength, and he was often referred to as the "leader of the pack." Other reindeer that begin with "D" include Dasher, Dancer, and Douglas, who were all also part of Santa's original team.