Mark Moshe Kasher (born July 6, 1979) is an American stand-up comedian, writer and actor based in the Los Angeles area. He is the author of the 2012 memoir Kasher in the Rye: The True Tale of a White Boy from Oakland Who Became a Drug Addict, Criminal, Mental Patient, and Then Turned 16. In 2009, iTunes named Kasher "Best New Comic" and his comedy album Everyone You Know Is Going to Die, and Then You Are! was ranked one of the top 20 comedy albums on iTunes that same year. He was also named "Comic to Watch in 2010" by Punchline Magazine.

Born in Queens, New York, Kasher moved to Oakland, California with his mother and brother when he was one year old. Kasher grew up in North Oakland's Temescal and Piedmont Avenue neighborhoods, and his family lived mostly on disability assistance and food stamps. A son of deaf parents, Kasher worked as a sign-language interpreter from the age of 17. His parents met at the World Games for the Deaf in 1967 and split up when Kasher was nine years old.

When Kasher was four years old, his father Steven, a former painter who was born to secular, communist Jewish parents, became a Hasidic Jew in the Satmar community in Brooklyn; Steven's grandfather, originally from Hungary, was a New Square Skverter Hasid. Kasher regularly spent summers with his father in Sea Gate, Brooklyn until his death — Kasher was 20 at the time. His father lived with Gaucher's disease. Kasher's brother is a rabbi.

In his autobiography Kasher in the Rye: The True Tale of a White Boy from Oakland Who Became a Drug Addict, Criminal, Mental Patient, and Then Turned 16, Kasher wrote about having been moved in and out of mental institutions from the age of four and using drugs from the ages of 12 to 16. He was kicked out of four different high schools. In an interview with SanDiego.com, Kasher described himself as "pretty straight edge," stating that he has been clean "since I was very young." He earned his G.E.D. at age 16 and later became a sign-language interpreter.

Kasher attended community college in the Bay Area, where he studied theater and wrote several long-form monologues. He later transferred to the University of California, Santa Barbara, where he graduated with a degree in religious studies and minored in Jewish studies. Before his career in comedy, Kasher had considered becoming a college professor in Jewish history.

In 2001, Kasher attended an open mic comedy night in New York which included a performance by Chelsea Peretti, a comedian and writer with whom Kasher had attended junior high school in Oakland. After seeing her perform, Kasher asked Peretti to take him along on future performances, offering to perform with her. For his first performance, she took him to an open mic at the Luggage Store Gallery in San Francisco.

In the early 2000s, Kasher performed mainly in the Bay Area, regularly performing at the Punch Line and Cobb's comedy clubs in San Francisco. In the mid to late 2000s, he participated in many comedy shows with fellow comedians Brent Weinbach and Alex Koll. In 2008 Kasher moved to Los Angeles.

2009 marked a significant year in Kasher's comedy career. He was named "Best of Fest" at that year's Aspen Rooftop Comedy Festival; his performance in Aspen garnered him an invitation to the Just For Laughs comedy festival in Montreal that same year. This was followed by an appearance on the Comedy Central series Live at Gotham. Kasher had also released his comedy album Everyone You Know Is Going to Die, and Then You Are! through Rooftop Comedy Productions in April 2009; near the year's end the album was deemed one of the top 20 comedy albums of 2009 on iTunes. Kasher was also recognized by iTunes as the Top New Comedy Artist of 2009.