William Eston Garretson (born August 24, 1949) was the caretaker of the Polanski residence at the time of Sharon Tate's murder by the Charles Manson "Family". A native of Lancaster, Ohio, Garretson stayed in a small cottage behind the main house. On the morning after the murders, he was arrested on charges of suspicion of murder, but was subsequently released.

When questioned, Garretson told police he had heard nothing outside at the time of the murders, because he had been listening to music; a police spot-check found this plausible, as recounted in Helter Skelter. However, in a 1990s E! Networks documentary about Sharon Tate's death, Garretson changed his story, stating on camera that he had first heard noises like firecrackers, and thought it was a prank pulled by Steven Parent, who had just departed. (As it turned out, the sounds were of Charles "Tex" Watson shooting Parent with a pistol.) When shouting and screams followed a few minutes later, Garretson hid in the cottage, not wanting to become involved, or be another victim. Garretson claimed on the TV program that he looked out from a window in the cottage to see a woman (Abigail Folger) being chased by another (Patricia Krenwinkel). Then Garretson heard Folger say she was already dead, which understandably confused Garretson even more.

After returning to Ohio, Garretson visited California again, to testify in the Tate-LaBianca trial. He had recurring nightmares about the murders, but after revisiting the house and seeing different tenants in residence, the nightmares subsided.