Russell Wendell Simmons (born October 4, 1957) is an American entrepreneur, writer and record executive. He co-founded the hip-hop label Def Jam Recordings, and created the clothing fashion lines Phat Farm, Argyleculture, and Tantris. He has promoted veganism and a yoga lifestyle, and published books on lifestyle, health, and entrepreneurship. Simmons' net worth was estimated at $340 million in 2011.

After producing or managing artists such as Kurtis Blow, Run DMC, Whodini, and Jimmy Spicer, Simmons joined forces with producer Rick Rubin to found Def Jam Recordings. Under Simmons' leadership as chairman, Def Jam signed acts including Beastie Boys, Public Enemy, LL Cool J, Jay-Z, DMX, and Kanye West. From 1992 to 1997, he also produced the Def Comedy Jam television program.

In 2017, Simmons was publicly accused of sexual assault by multiple women; he denied the allegations. Following these allegations, Simmons stepped down from his various business roles and charities, including his position at Def Jam.

Russell Wendell Simmons was born in the Hollis neighborhood of New York City's Queens borough on October 4, 1957. His father was a public school administrator and his mother was a park administrator for the New York City Parks and Recreation Department. His brothers are painter Daniel Simmons Jr. and Joseph Simmons (better known as Rev Run of Run-DMC fame). In 1975, after graduating from August Martin High School, Simmons briefly attended the City College of New York in Harlem where he met a young DJ/Bboy, Kurt Walker, who influenced him to participate in the hip hop phenomenon. Upon hearing Eddie Cheeba perform in Harlem in 1977, Simmons knew that hip hop would be his career. Simmons stated, "Hearing Cheeba in '77 made me feel like I had just witnessed the invention of the wheel." In 1979, Simmons met Robert Ford Jr., who began taking him to industry events and teaching him about the music business. Simmons would later credit Ford as his "guru".

Simmons co-founded Def Jam in 1984 with Rick Rubin, after many mergers, Simmons sold his share of the company for $120 million to Universal Music Group in 1998. Simmons co-produced and appeared in the 1985 film Krush Groove. Simmons' company, Rush Communications Inc., includes over ten businesses and three non-profits. Simmons, with his partner Stan Lathan, has also produced television hits HBO's Def Comedy Jam and Def Poetry Jam, and currently has a development deal with HBO. In 1996, Simmons co-produced the hit film The Nutty Professor, starring Eddie Murphy. In 1997, Simmons co-produced the film Def Jam's How to Be a Player, starring Bill Bellamy. In 2003, Simmons co-founded RushCard, a prepaid debit card provider.

In 1992, Simmons launched the clothing line Phat Fashions LLC using the Phat Farm and Baby Phat labels. When Simmons first created Phat Fashions LLC, the clothing line was sold in a shop in the SoHo district of Manhattan. Simmons's connections with well-known rap artists helped to promote the clothing line to a wide audience. The influence of designers such as Ralph Lauren and Tommy Hilfiger gave the clothing line a classic look and feel. Phat Fashions encompassed hip hop clothing for women and children, as well as men, and grew into a lifestyle brand with the addition of jewelry, perfume, and other merchandise. Phat Fashions LLC sold merchandise in two stores in New York and Montreal, as well as online at www.phatfarm.com. In addition, the clothing line was carried by some 3,000 retailers in the United States.

In 2001, "Hip-Hop Minister" and former Nation of Islam minister Conrad Tillard feuded with Simmons, accusing him of stoking violence by allowing the frequent use of words such as "nigga" and "bitch" in rap lyrics. Tillard then organized a summit in Harlem over what he viewed as negative imagery in hip hop. Simmons organized a counter-summit, urging the public not to "support open and aggressive critics of the hip-hop community".

In 2002, Simmons launched his first Broadway venture, Russell Simmons' Def Poetry Jam on Broadway.