Thomas Jacob "Jack" Black (born August 28, 1969) is an American actor, comedian, and musician. He makes up one half of the comedy and heavy metal music duo Tenacious D. The group has two albums and a full-length film. His acting career is extensive, starring primarily as bumbling, cocky, but internally self-conscious outsiders in comedy films. He is a member of the Frat Pack, a group of comedians who have appeared together in several Hollywood films, and has been nominated for a Golden Globe award. He has also won an MTV Movie Award, and a Nickelodeon Kids Choice Award.

Black was born in Santa Monica, California, the son of two satellite engineers, Judith (née Cohen) and Thomas William Black. His mother worked on the Hubble Space Telescope. Jack Black's mother is Jewish and his father converted to Judaism; Black was thus raised as a Jew. On The Tonight Show he said his surname may come from the Scottish occupational name Blacksmith. His parents divorced when he was 10. Jack Black had a Bull Mastiff/Rottweiler mix named Chico. Chico died of parvovirus soon after Jack's parents divorced. Black moved to Culver City with his father and frequently visited his mother’s home until the end of his first year of college at UCLA when his father’s family moved to France. As a child, Black appeared in an early Activision Pitfall! for the Atari 2600 commercial in 1982, which was later shown during an appearance on Jimmy Kimmel Live and again on The Tonight Show with Jay Leno.

When he entered high school, his parents suggested that he should transfer to the Poseidon School, a private secondary school engineered specifically for students struggling in the traditional school system. Black eagerly accepted the proposition, afraid that he would only be bullied if he remained in public school.