Descriptive term applied to an unnamed KAOS agent who operates the Washington Animal Spa where he brainwashes the pets of important government officials into killing their masters.
After learning that "Stanley Maxwell", the owner of one of the spa's boarders, is actually CONTROL agent Maxwell Smart, the Beastmaster uses the dog (actually Fang undercover) as bait to draw Max into a trap, in turn using him as bait for an attempt on the Chief's life using a bomb set to explode at the sound of Fang's bark.
The Beastmaster meets his end when Max and 99 are able to get Fang to drop the Beastmaster's bomb down an elevator shaft to the basement where he and his assistant are waiting.
Note that the term Beastmaster appears in the credits but is not used in the episode itself.
Portrayed by Oscar Beregi [Episode #23: "I'm Only Human"].