Gary Leon Ridgway (born February 18, 1949), known as the Green River Killer or the Green River Strangler, is an American serial killer who was convicted of murdering forty-nine women between 1982 and 1998 in the northwestern United States. At the time of his arrest in 2001, he was believed to be the most prolific serial killer in United States history, according to confirmed murders.

Most of Ridgway's victims were alleged sex workers or other women in vulnerable circumstances, including underage runaways. Before his capture, media outlets nicknamed him the Green River Killer or Green River Strangler due to his first five victims being found at the Green River in Washington State. Ridgway strangled his victims, usually by hand, but sometimes using ligatures. After strangling them, he would dump their bodies in forested and overgrown areas, often returning to the bodies to engage in acts of necrophilia.

Ridgway had been a suspect in the Green River case since 1982; however, investigators were unable to link him to the murders at that time. Later advances in DNA profiling allowed investigators to definitively link Ridgway to the murders, and he was arrested on November 30, 2001, as he was leaving the Kenworth truck factory where he worked in Renton, Washington. As part of a plea bargain wherein he agreed to disclose the locations of still-missing women, he was spared the death penalty and received a sentence of life imprisonment without the possibility of parole.