Rousey was born in Riverside, California, the youngest of three daughters of AnnMaria De Mars (née Waddell) and Ron Rousey, for whom Rousey was named. Her mother, a decorated Judoka, was the first American to win a World Judo Championship (in 1984). Her maternal grandfather was Venezuelan and was of part Afro-Venezuelan ancestry; her maternal great-grandfather was Dr. Alfred E Waddell, a Trinidadian who emigrated to Canada and became one of the first black physicians in North America. Her other roots are English and Polish. Her stepfather is an aerospace engineer. Her biological father, after breaking his back sledding with his daughters and learning that he would be a paraplegic, committed suicide in 1995, when Rousey was eight. AnnMaria pursued a Ph.D. in educational psychology at the University of California, Riverside as her daughters grew up.

For the first six years of her life, Rousey struggled with speech and could not form an intelligible sentence due to apraxia, a neurological childhood speech sound disorder. This speech disorder was attributed to being born with her umbilical cord wrapped around her neck. When Rousey was three years old, her mother and father moved from Riverside, California, to Jamestown, North Dakota, to obtain intensive speech therapy with specialists at Minot State University.

Rousey dropped out of high school and later earned a G.E.D. She was raised between Southern California and Jamestown, North Dakota, retiring from her judo career at 21 and starting her MMA career at 22 when she realized that she did not want to spend her life in a conventional field of work