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 48 and 90 kg (106 and 198 lb), Sitka deer are characteristically smaller than other subspecies of mule deer. Reddish-brown in the summer, their coats darken to a gray-brown in mid- to late August. They are also good swimmers, and can occasionally be seen crossing deep channels between islands. Their average lifespan is about 10 years, but a few are known to have attained an age of 15.