Allan Aaron Masur (June 4, 1924 - July 17, 2005) was the founder of Congregation B'nai Olam on Fire Island and one of the early leaders of Congregation Beth Simchat Torah in New York City.

Allan Aaron Masur was a native New Yorker. He graduated Phi Beta Kappa from City College and received a law degree from Columbia University in 1950. He then began practicing law in New York City, which he continued throughout his life.

Masur first visited Fire Island in 1946, after service in the U.S. Army during World War II. According to reports, he attended a cocktail party in Cherry Grove where he met renowned artists and writers and got a glimpse of a very different style of life. Typical of this day, he was closeted and dated women in public. He returned to Fire Island in 1960 to visit friends who lived in The Pines. After several more visits, he purchased a home there in 1962. The following year he purchased a lot on the bay where he eventually built a larger home.

When Cinematheque at 80 Wooster Street was fading out in the 1970s, Jonas Mekas’s dream of an academy devoted to avant-garde film was saved when funding from Jerome Hill and Allan Masur enabled Mekas to create The Anthology Film Archives, which was to operate independently within Joseph Papp’s Public Theater.

Masur attended religious services at Temple Emmanuel, a large synagogue on the Upper East Side. In 1973, he decided to remain on Fire Island and celebrate the Jewish High Holidays among friends, so he hosted services at his home. That first year 30 persons attended services; two years later 200 people attended. Masur was pleased that these services provided an opportunity for a number of gay men to reconnect with their Jewish heritage and tradition. Masur's efforts grew into Congregation B'nai Olam, which moved into another building, the old Community House on Coast Guard Walk, in 1976.

Masur began serving as legal counsel to the recently-formed Congregation Beth Simchat Torah (CBST), New York's GLBT synagogue, in 1974. He assisted the congregation's board of directors in their fund raising efforts. When the congregation outgrew its meeting space at the Church of the Holy Apostles in Chelsea, Masur helped secure and negotiate terms for rental of commercial space in the Westbeth Artists Housing Complex in Greenwich Village in 1975, where the congregation still meets. CBST honored Masur with the Chesed Award in 1993 in recognition of his lifetime of achievement for the congregation.

Masur died on July 17, 2005, survived by his partner, Jimmy Stewart.