William Hopkins was born in Greenville, South Carolina, in 1942. At the age of nine months he was adopted by a couple who were unable to conceive their own. Growing up, he was called "Billy". His adoptive father worked in a mill in Taylors, South Carolina. When his father was 39, Billy was present with his mother when he died of a heart attack on the porch of the family's home. Unable to remain in their house, a month later the two of them moved to a new residence in nearby Ware Shoals, where his grandfather and uncles worked in another mill. His mother eventually remarried to a man whose last name was Davis. Hopkins did not get along with his new stepfather and the two got into numerous arguments, some serious. After running away from home a few times, he was sent to live with grandparents out in the country and while there he learned that he had been adopted because his adoptive mother could not bear children. At age 12, he met his birth mother for the first time, who lived in a South Carolina mill town called Lockhart, and also his half-sisters and a half-brother.
Billy led a troubled life as a youngster, with numerous instances of truancy, minor crimes, and a stay at a reform school. He dropped out of school at 16 just before his 17th birthday and joined the United States Army, where he was assigned to the 101st Airborne division. He was based at Fort Jackson, Fort Gordon and Fort Pope, before being shipped off to Korea, where he served for nine months. After his military service, William "Billy" Hopkins began dating a girl named Norma, who he married at about age 18, and they had a daughter named Jane.
Hopkins became interested in pursuing an acting career, which his wife disapproved of, and she left him, taking their daughter with her. After appearing in some area plays, he received a scholarship to study acting and stage production at the Pioneer Playhouse in Kentucky, where he soon moved. While there he began dating a girl who was a Miss Mississippi. From Kentucky, he made his way to New York City to act in more stage plays. After New York, he moved to Hollywood with his cousin's boyfriend, who wanted to be a stuntman. In Hollywood, he earned a living parking cars while studying at the Actors Studio, where one of his classmates was future Oscar winner Martin Landau.Explaining in a 2012 magazine interview how he got his first name "Bo," he said:
William Hopkins is my real name. Billy when I was growing up. When I went to New York, "Bus Stop" was my first off-Broadway play, and the character that I played was named "Bo." The producers wanted me to change my name, and since I wanted to keep my last name, we agreed to change the first. That's how it became "Bo."— Bo Hopkins, Shock Cinema, "An Interview with Actor Bo Hopkins", Number 42, June 2012.
Hopkins is currently married to Sian Eleanor Green (1989 to present). After six years of professional inactivity, Hopkins has returned to acting, reading scripts, and is writing his autobiography.