Del Martin (born May 5, 1921) and Phyllis Lyon (born 1924) are an American lesbian couple known as feminist and gay-rights activists.

Martin and Lyon have been leaders of the lesbian and feminist movements since the 1950s. They met in Seattle in 1950, and by 1952 their friendship had evolved into a life partnership that has lasted for more than 50 years. In 1953, they moved to San Francisco, California where, in 1955, they formed the homophile organization the Daughters of Bilitis (DOB). Lyon was the first editor of DOB's newsletter, The Ladder, beginning in 1956.

Martin and Lyon have been active in the National Organization for Women (NOW) since 1967. Martin is the author of Battered Wives (1976) and the co-author of Lesbian/Woman with Lyon (1972). The Lyon-Martin Women's Health Services, founded in San Francisco in 1979, is named for them.

In 1989, Martin and Lyon joined Old Lesbians Organizing for Change. In 1995 Martin and Lyon were named delegates to the White House Conference on Aging. Martin by Senator Dianne Feinstein and Lyon by Congreswoman Nancy Pelosi. In 2003 filmmaker Joan E. Biren released a documentary film on the couple, No Secret Anymore: The Times of Del Martin and Phyllis Lyon.

On February 12, 2004, Martin and Lyon were granted a marriage license, the first in a series of marriage licenses issued to same-sex couples in the United States by various local governments in 2004. The license was granted in violation of California state law by the City and County of San Francisco in an act of civil disobedience.

The marriages were voided on August 12 of that year. Ms. Lyon reacted, saying:

"Del is 83 years old and I am 79. After being together for more than 50 years, it is a terrible blow to have the rights and protections of marriage taken away from us. At our age, we do not have the luxury of time."