Theodore John "Ted" Kaczynski (born May 22, 1942 in Evergreen Park, Illinois) is an American mathematician who was known as the Unabomber. Between 1978 and 1995, Kaczynski engaged in a nationwide bombing campaign against people involved with modern technology, planting or mailing numerous home-made bombs, ultimately killing a total of three people and injuring 23 others.

Kaczynski was born and raised in Evergreen Park, Illinois, a Chicago suburb. Kaczynski was accepted to Harvard University at the age of 16. He earned an undergraduate degree. He then earned a PhD in mathematics from the University of Michigan. He became an assistant professor at the University of California, Berkeley in 1967 at age 25. He resigned two years later.

In 1971, he moved to a cabin without electricity or running water, in Lincoln, Montana. He lived there while learning survival skills. From 1978 to 1995, Kaczynski sent 16 bombs to targets including universities and airlines, killing three people and injuring 23.

Kaczynski sent a letter to The New York Times on April 24, 1995. He promised "to desist from terrorism" if the Times or the Washington Post published his manifesto.

Kaczynski was arrested in his cabin on April 3, 1996. His brother, David, called the police so that they could arrest him. He pleaded guilty of his crimes on January 22, 1998. He is an inmate of ADX Florence, Fremont County, Colorado. On December 14th, 2021, he was moved from ADX Florence to the Federal Medical Center, Butner, North Carolina, for his health. On February 7th, 2022, a pen pal of Kaczynski announced that he had terminal cancer of the skin.

Kaczynski has written many books, Industrial Society and It's Future, Anti-Tech Revolution: Why and How, and Technological Slavery are his most famous. Industrial Society and It's Future is best known as the "Unabomber's Manifesto".