Ronald Kray (24 October 1933 – 17 March 1995) alongside his identical twin brother Reginald Kray (more commonly referred to as Ronnie and Reggie) were English gangsters from London who were heavily involved in organised crime from the late 1950s until their arrest in 1968.

Their gang, known as the Firm, was based in Bethnal Green, where the Kray twins lived. They were involved in murder, armed robbery, arson, protection rackets, gambling and assaults. At their peak in the 1960s, they gained a certain measure of celebrity status by mixing with prominent members of London society, being photographed by David Bailey and interviewed on television.

The Krays were arrested on 8 May 1968 and convicted in 1969 as a result of the efforts of detectives led by Detective Superintendent Leonard "Nipper" Read. Each was sentenced to life imprisonment. Ronnie, upon being certified insane, was committed to Broadmoor Hospital in 1979 and remained there until his death on 17 March 1995 from a heart attack.