Born Myra Maybelle Shirley, Belle and her family lived in Carthage, Missouri until the outbreak of the Civil War. Her father owned an inn, and she was educated at the Carthage Female Academy. Belle also received piano lessons as a girl.
Her family moved to Sycene, Texas in 1864 because Carthage had become too dangerous due to Civil War tensions. Belle's brother, Bruce, was killed by Union soldiers in Missouri the same year while he was with Confederate sympathizers. Many of Belle's Missouri acquaintances migrated to Texas during this time, including Jesse James and the Younger brothers (Cole Younger was one of her childhood friends). Historians believe that Belle became involved with these outlaws during this period of her life, as these outlaws often hid at the Shirley's farm.
Belle married James C. "Jim" Reed in 1866, and she had her first child, Rosie Lee "Pearl," in 1868. Some historians believe that Pearl's father was actually Cole Younger, though there is no proof to that claim. At the beginning of their marriage, Jim tried to support his family as a farmer, but fell into the company of the Starr clan in the Indian Territory (Oklahoma). In 1869, Jim shot a man who was believed to have murdered Jim's brother, and he, Belle, and Pearl fled to California. After more problems with the law, the family was forced to return to Texas shortly after the birth of their son Ed in 1871.
In 1873, Jim robbed a wealthy farmer in the Indian Territory, gaining thousands of dollars worth of gold coins. However, he had to run to Paris, Texas to hide, and Belle took the children to Dallas. She became famous at this time, dressing in very stylish clothing, carrying pistols, and spending the majority of her time in saloons, drinking and gambling.
Jim was shot to death in 1874 in Paris, Texas shortly after he robbed a stagecoach.
To support her family, Belle put her children in the care of relatives and joined the Starr clan in the Indian Territory. At this time, her career as an accomplice and organizer of horse thieves and bootleggers began, and she married a member of the clan, Sam Starr, in 1880.
She sentenced to one year in prison in 1883, but due to her model behavior, she and her husband were allowed to return home after only nine months. Her life as an outlaw continued shortly following her release. Though arrested many times, she never went to jail again.
In 1886, Samuel Starr was shot, and Belle was a widow again. Though she had several love affairs for the last few years of her life, she never remarried. Two days before her 41st birthday, Belle Starr was shot to death by an anonymous assassin. The year of her death, 1889, she became famous due to a dime novel, Bella Starr, the Bandit Queen, or the Female Jesse James, which fictionalized her life.