Family
- father Michael Horowitz: Born c. 1939; owner of Flashback Books, a store specializing in the writings of the counterculture; book archivist for Timothy Leary; married Ryder's mother in 1982; originally from Brooklyn and graduate of NYU
- mother Cindy Palmer Horowitz: Born c. 1941; previously married with two children; wed Ryder's father in 1982
- godfather Timothy Leary: Born in 1920; coined phrase "Turn on, tune in, drop out" in 1960s; died in 1996
- half-sister Sunyata Palmer: Born c. 1967; from mother's first marriage; name comes from The Tibetan Book of the Dead
- half-brother Jubal Palmer: Born c. 1969; from mother's first marriage; name came to his mother Cindy in a dream
- brother Yuri Horowitz: Born c. 1976; named after first Russian cosmonaut Yuri Gagarin
Companions
- Companion Blake Sennett: Rilo Kelly guitarist; met while filming "Water Pill"
- Companion Page Hamilton: Dated in 2003; no longer together
- David Pirner: lead singer for the Minneapolis-based grunge rock group Soul Asylum; together from 1993 to 1996
- Jimmy Fallon: reportedly dated in spring 2001
- Johnny Depp: born on June 9, 1963; engaged to be married as of February 1990; had "Winona Forever" tatooed on his arm (since partially removed); separated in 1993; Ryder later said of their breakup: "I was just really young. I don't know what his excuse is, but that's mine"
- Matt Damon: introduced by Gwyneth Paltrow at a New Year's Eve party on December 31, 1997; separated in April 2000
- Peter Yorn: reportedly dated in late 2001
- Companion conor oberst: Reportedly dated in 2003; no longer together
- Companion Henry-Alex Rubin: Dated in 2006; no longer together
