John Sinclair (October 2, 1941 – April 2, 2024) was an American poet, writer, and political activist from Flint, Michigan. Sinclair's defining style is jazz poetry, and he released most of his works in audio formats. Most of his pieces include musical accompaniment, usually by a varying group of collaborators dubbed Blues Scholars.

As an emerging young poet in the mid-1960s, Sinclair took on the role of manager for the Detroit rock band MC5. The band's politically charged music and its Yippie core audience dovetailed with Sinclair's own radical development. In 1968, while still working with the band, he conspicuously served as a founding member of the White Panther Party, a militantly anti-racist socialist group and counterpart of the Black Panther Party. Arrested for distribution of marijuana in 1969, Sinclair was given ten years in prison. The sentence was criticized by many as unduly harsh, and it galvanized a noisy protest movement led by prominent figures of the 1960s counterculture. He was freed on March 9, 1972, by the Michigan Supreme Court when the possession of marijuana law was declared unconstitutional.

He was indicted for an alleged terrorist bombing of a covert CIA office. That matter involved substantial litigation – his case against the government for illegal domestic surveillance was successfully pleaded to the US Supreme Court in United States v. U.S. District Court (1972). It took the form of a Writ of Mandamus, which was won at the United States Court of Appeals for the Sixth Circuit and an appeal on certiorari to the Supreme Court. The wiretap evidence was suppressed, and the criminal case dropped.

Sinclair eventually left the US and took up residency in Amsterdam. He continued to write and record and, from 2005, hosted a regular radio program, The John Sinclair Radio Show, as well as producing a line-up of other shows on his own radio station, Radio Free Amsterdam.

Sinclair was among the first people to purchase recreational marijuana when it became legal in Michigan on December 1, 2019.