The Hunters are a cult-like band of renegade Watchers formed by their leader and fellow former Watcher named James Horton, and an antagonistic organization in the episode "The Hunters" of the TV series Highlander: The Series. The Hunters broke the principles of the Watcher Society and began taking heads of Immortals on their own due to these fanatical mortals' beliefs that all immortals are abominations and they must be destroyed.
The Hunters believe that all Immortals are evil and "an abomination in the eyes of God." Consequently, the Hunters use the Watcher Chronicles to hunt and kill any and all Immortals they can isolate, in order to make sure no one ever wins The Prize. After a misstep with the couple, Jacob and Irena Galati, they learned to never behead one immortal in the presence of another.
The Hunters mimic the Watcher Society, albeit on a smaller scale. One Hunter is usually the ringleader in an immortal hunt, with several others providing backup. Their most noteworthy victim was the reformed warlord, the peace-loving Father Darius.
Perhaps unsurprisingly, they are almost all young people, both impressionable and likely still overwhelmed by the existence of Immortals, and the often-bloody past that exposes them to.
With Horton dead, the Hunter group is all but non-existant. However, the occasional follow-up group has been known to pop up, usually lead by one of Horton's associates.
In medieval times, Duncan Macleod and Hugh Fitzcairn recalled being accosted by mysterious assassins bearing the Watchers' tattoo. That said, the Hunters seemed like more of a modern development, with Horton perhaps seizing on resentment that had always been in the ranks, like Adolf Hitler did for anti-Semitism and other long-simmering hatreds in Europe. Also, whether these past assassins had anti-Immortal sentiments or other motivations for the attack is never established. Both Macleod and Fitzcairn had many enemies, as did Duncan's kinsman Connor, and Fitzcairn was often a reckless ladies' man.