Thomas Emmet Hayden (December 11, 1939 – October 23, 2016) was an American social and political activist, author, and politician. Hayden was best known for his role as an anti-war, civil rights, and intellectual activist in the 1960s, becoming an influential figure in the rise of the New Left. As a leader of the leftist organization Students for a Democratic Society, he wrote the Port Huron Statement, helped lead protests at the 1968 Democratic National Convention, and stood trial in the resulting "Chicago Seven" case.

In later years, he ran for political office numerous times, winning seats in both the California State Assembly and California State Senate. At the end of his life, he was the director of the Peace and Justice Resource Center in Los Angeles County. He was married to Jane Fonda for 17 years and is the father of actor Troy Garity.

Tom Hayden was born in Royal Oak, Michigan, to parents of Irish ancestry, Genevieve Isabelle (née Garity) and John Francis Hayden. His father was a former Marine who worked for Chrysler as an accountant and was also a violent alcoholic. When Hayden was 10, his parents divorced, and his mother raised him. Hayden attended a Catholic elementary school, where he read out loud to nuns and "learned to fear hell."

Hayden grew up attending a church led by Charles Coughlin, a Catholic priest noted for his anti-Semitic teachings, and who was also known nationally during the time of The Great Depression as the "radio priest". Hayden's dismay with Coughlin caused him to break with the Catholic Church as a teenager.

Hayden attended Dondero High School in Royal Oak, Michigan. He served as the editor for the school newspaper, and in his farewell column in the newspaper, he used the first letter of successive paragraphs to spell "Go to hell". As a result, when he was graduated in 1956, he was banned from attending his graduation ceremony and only received a diploma.

Hayden then attended the University of Michigan, where he was editor of the Michigan Daily. At the National Student Association convention in Minneapolis in August 1960, Hayden witnessed a dramatic intervention by Sandra Cason. To a standing ovation she turned back a motion denying support for sit-ins in the struggle against racial segregation: “I cannot say to a person who suffers injustice, ‘Wait,’ And having decided that I cannot urge caution, I must stand with him.” Alan Haber of the fledgling Students for a Democratic Society (SDS) recruited her on the spot. Stirred by her "ability to think morally [and] express herself poetically," Hayden soon followed her into the left-wing grouping. They married in October the following year.

Despite being attacked by a mob in McComb, Mississippi, while covering the Freedom Rides for the National Student News, Hayden himself became a Freedom Rider. On December 10, 1961, the Haydens participated in one of the many “freedom rides” taking place in response to the 1960 Boynton v. Virginia decision. After being arrested for his role in the Freedom Rides, Hayden began writing the SDS manifesto from jail in Albany, Georgia.

Refined and adopted at the first Students for Democratic Society (SDS) convention in June 1962, the Port Huron Statement called for a "new left" committed, in the spirit of participatory democracy, to "deliberativeness, honesty [and] reflection." The sponsoring League for Industrial Democracy (LID) took immediate issue. Although The Statement did express regret at the "perversion of the older left by Stalinism," it omitted the LID's standard denunciation of communism. Hayden was called to a meeting where, refusing any further concession, he clashed with Michael Harrington, as he later would with Irving Howe.