英国古代牧羊犬（英语：Old English Sheepdog）是一种以放牧家畜和宠物为目的而培育的犬种。英国古代牧羊犬的特征是灰白的长毛和头上盖眼的毛发。

幼犬出生时的全身覆盖着熊猫般的纯黑和纯白色短毛，只有在退去幼毛之后，银灰色的长毛才会出现。若在法律允许的国家，通常古代牧羊犬的尾巴，会在幼犬时于第一个尾关节处切断。这种手续会产生类似熊猫的尾部，英文称作bobbing 或 docking。因为许多国家禁止这种习惯的关系，没有断尾的古代牧羊犬，反而越来越常见。目前英国养狗俱乐部并不鼓励合法切除古代牧羊犬的尾巴，只规定参展犬才需要断尾。

The Old English Sheepdog (OES) is a large breed of dog which was developed in England from early herding types of dog. The Old English Sheepdog can grow a very long coat, with fur covering the face and eyes. Obsolete names of the breed include Shepherd's Dog and bob-tailed sheep-dog. It is still nicknamed Bob-tail (or Bobtail) because historically, the tail was traditionally docked in this breed.