William Lawrence Boyd was an American film actor who is known for portraying the cowboy hero Hopalong Cassidy.

Hopalong Cassidy is a fictional cowboy hero created in 1904 by the author Clarence E. Mulford, who wrote a series of short stories and novels based on the character. Mulford portrayed the character as rude, dangerous, and rough-talking. He was shot in the leg during a gun fight which caused him to walk with a little "hop", hence the nickname.