The first mediaeval military religious order, the Templars were formed c1118 in Palestine to patrol and protect pilgrim routes from bandits. They became a major order in Palestine and Europe before being put on trial in 1307 for heresy and suppressed in 1312. Their Grand Master was burned at the stake in 1314, leading to many legends that they continued as an underground cult.

Alternate definition #1: A branch of the Freemasons that claims to continue the ideals of the mediaeval Templars.

Alternate definition #2: A Mexican narco-terrorist group that first appeared in the Michoacan state in March 2011.