Gary Barnett is the founder and president of Extell Development, one of the most active development companies in New York City.

Barnett made his fortune in the diamond trade. He became active through Extell in the 1990s, ramping up his number of projects, both residential and commercial, significantly during the pre-recession boom. On the residential side, Barnett's projects have included the 1,000-foot One57; the 37-story Ariel East and 31-story Ariel West condos at 100th Street and Broadway; the Lucida rentals and condos (more than 170 apartments in all, some as big as five bedrooms) at 151 East 85th Street; the 26-unit 995 Fifth Avenue, where some of the condos occupy an entire floor; the 271-unit Rushmore at 80 Riverside Boulevard; and the 150-unit Aldyn nearby at 60 Riverside Boulevard.

Barnett is also the developer of the 1,550-foot supertall at 217 West 57th Street along Billionaires' Row dubbed Central Park Tower, the tallest residential building in the world (as of 2021). The 179-unit tower has a projected sellout of $4 billion, making it the most expensive condominium project in New York City. Closings kicked off in early 2021.

On the commercial side, Barnett's projects include the 750,000-square-foot, 34-story International Gem Tower, which topped out in March 2012, and the 1.5 million-square-foot World Product Centre at 555 West 33rd Street, the site of the old Copacabana.

Born Gershon Swiatycki, Barnett grew up on Manhattan's Lower East Side and earned a math degree from Queens College and a master's in economics from Hunter College.