The Mattachine Society of New York, Inc. was an early gay rights organization.

It was founded by Harry Hay and first met in Los Angeles on November 11, 1950 with Harry, Rudi Gernreich, Bob Hull, Chuck Rowland, and Dale Jennings in attendance, but was not incorporated until 1961. Several other related organizations were formed shortly afterward in New York, Boston, Chicago, Denver, the District of Columbia, and Philadelphia. The primary goal of the society was to encourage the public to view homosexuals as a persecuted minority rather than mental deviants.

All of the Mattachine founders were affiliated with Communism and based the organization on the cell structure of the American Communist Party. As the Red Scare progressed the communist associations concerned some members and supporters, and Hay stepped down as the society's leader. Others who were similarly ousted were replaced by comparatively conservative leaders.

Although Harry Hay claimed 'never to have even heard' of the earlier gay liberation struggle in Germany - by the people around Adolf Brand, Magnus Hirschfeld and Leontine Sagan - he is known to have talked about it with German emigres in America including Rudi Gernreich.

The Mattachine Society's goal was to liberate the oppressed homosexual community and provide a variety of services to the gay community, including referral services for legal and other professionals, and counselling. They also lobbied for the repeal of sodomy laws and other laws that gay people considered discriminatory. It published The Mattachine Review.

It was associated with other groups in ECHO (East Coast Homophile Organizations ). There was an amicable split from Mattachine in 1952, called ONE, Inc.. ONE admitted women, and together it and Mattachine provided vital help to the Daughters of Bilitis in the launching of their newsletter The Ladder: a lesbian review in 1956. The Daughters of Bilitis was the counterpart lesbian organisation to the Mattachine Society, and the two organisations worked together on some campaigns. Bilitis came under attack in the early 1970s for 'siding' with Mattachine rather than with the new seperatist feminists.

During the 1960s, Mattachine was one of the foremost gay rights groups in the United States. But following the Stonewall riots of 1969, it became increasingly seen as stodgy and traditional, and not willing enough to be confrontational. It lost support, and fell prey to infighting. Eventually it closed due to impending bankruptcy, and was disbanded in January of 1987.

The Mattachine Society was named after Mattacino (or the Anglicized Mattachino), a character in Italian theater. Mattacino was a kind of court jester, who would speak the truth to the king when nobody else would. The "mattachin" (from Arabic mutawajjihin—"mask-wearers") were originally Moorish (Hispano-Arab) sword-dancers who wore elaborate, colorful costumes and masks.