The Sitka deer or Sitka black-tailed deer (Odocoileus hemionus sitkensis), is a subspecies of mule deer (Odocoileus hemionus), similar to the Columbian black-tailed subspecies (O. h. colombianus). Their name originates from Sitka, Alaska, and it is not to be confused with the similarly named sika deer. Weighing in on average between , Sitka deer are characteristically smaller than other subspecies of mule deer. Reddish-brown in the summer, their coats darken to a gray-brown in the winter. They are also good swimmers, and can occasionally be seen crossing deep channels between islands. Their average life span is about 10 years but a few are known to have attained an age of 15.