Robert Alan Durst (April 12, 1943 – January 10, 2022) was an American convicted murderer, suspected serial killer and real estate heir. The eldest son of New York City real estate magnate Seymour Durst, he garnered attention as a suspect in the unsolved 1982 disappearance of his first wife, Kathleen "Kathie" McCormack; the 2000 murder of his longtime friend, Susan Berman; and the 2001 killing of neighbor Morris Black.

Acquitted of murdering Black in 2003, Durst did not face further legal action until his participation in the 2015 documentary miniseries The Jinx led to him being charged with Berman's murder. Durst was convicted in 2021 and sentenced to life imprisonment without parole. He was also charged with McCormack's murder shortly after his sentencing but died in 2022 before a trial could begin. Durst's conviction for Berman's murder was automatically vacated upon his death because his appeal was still pending.

Robert Alan Durst was born in New York City on April 12, 1943, and grew up in Scarsdale, New York. He was the eldest son of real estate magnate Seymour Durst and his wife, Bernice Herstein. His paternal grandfather, Joseph Durst, originally a Jewish tailor from Austria-Hungary, immigrated to the United States in 1902 and eventually became a real estate manager and developer, founding the Durst Organization in 1927. His three younger siblings were Douglas, Tommy and Wendy Durst.

When Durst was seven years old, his mother died by suicide after jumping from the roof of the family's Scarsdale home. He later claimed to have witnessed the act, asserting that moments before her death, his father walked him to a window from which he could see her standing on the roof. However, in a March 2015 New York Times interview, Durst's brother Douglas denied that he had witnessed the suicide. As children, Robert and Douglas underwent counseling for sibling rivalry; a 1953 psychiatrist's report on Durst, then ten years old, mentioned "personality decomposition and possibly even schizophrenia."

Durst attended Scarsdale High School, where classmates described him as a loner. He earned a bachelor's degree in economics in 1965 from Lehigh University, where he was a member of the varsity lacrosse team and the business manager of the student newspaper, The Brown and White. Later that year, Durst enrolled in a doctoral program at the University of California, Los Angeles, where he met Susan Berman, but eventually withdrew from the school and returned to New York in 1969.

Durst opened a small health-food store in Vermont in the early 1970s. He closed the store in 1973, when his father convinced him to return to New York and work in the Durst Organization. In 1992, due to Durst's erratic conduct, his father broke with tradition and appointed his second son, Douglas, to take over the company. As the firstborn, Durst felt entitled to run the company despite his disdain for it and accused Douglas of stealing what was rightfully owed to him. This resulted in Robert's estrangement from the rest of his family. He eventually sued for his share of the fortune, and was bought out of the family trust for $65 million in 2006.

For most of his adult life, Durst was the subject of investigation and speculation concerning three alleged crimes: the 1982 disappearance of his wife, Kathleen "Kathie" McCormack; the 2000 murder of his longtime friend, Susan Berman; and the 2001 death of his neighbor, Morris Black. Durst was ultimately tried and acquitted for murder in the Black case but was later convicted in the Berman case.

In late 1971, Durst met dental hygienist Kathleen McCormack. After two dates, he invited her to move into his home in Vermont, which she did in January 1972. After his father pressured him to return to New York to work at the Durst Organization, the couple moved to Manhattan, where they married on April 12, 1973.