Alvin Francis Karpis, was a Canadian–American criminal of Lithuanian descent known for being a leader of the Barker–Karpis gang in the 1930s. Nicknamed "Creepy" for his sinister smile and called "Ray" by his gang members, Karpis led the gang along with Fred Barker and Arthur "Doc" Barker. There were only four "public enemies" ever given the title of "Public Enemy #1" by the FBI and he was the only one to be taken alive. The other three, John Dillinger, Pretty Boy Floyd, and Baby Face Nelson, were all killed before being captured. He also spent the longest time as a federal prisoner at Alcatraz Federal Penitentiary, serving twenty-six years.

The Barker–Karpis Gang was one of the longest-lived criminal gangs during the Depression Era, spanning from 1931 to 1935. The gang was founded by Fred Barker and Alvin Karpis, and later joined by Fred's brother Arthur "Doc" Barker. Along with the three core members, the gang's network spanned up to 25 members at one point.