Karloff was born in Camberwell, London, to a father who was an Anglo-Indian diplomat and a mother who was of mixed French and German descent. He began his acting career in the United Kingdom in the early 1910s, appearing in stage productions and silent films. In 1919, he moved to Hollywood, where he initially struggled to find success.
He starred in many of Universal Studios' horror films of the 1930s, including The Old Dark House (1932), The Mask of Fu Manchu (1932), The Black Room (1935), and The Bride of Frankenstein (1935). In 1939, he played the role of Dr. Frankenstein in Son of Frankenstein, the third film in the Frankenstein series.
In the 1940s, Karloff continued to appear in horror films, but he also began to branch out into other genres, including comedy, westerns, and drama. He starred in such films as House of Frankenstein (1944), Abbot and Costello Meet Frankenstein (1948), and The Snake Pit (1948).
In the 1950s, Karloff's career began to decline, but he continued to appear in films and television shows until his death in 1969.
Karloff was married twice, first to Grace Radcliffe from 1915 to 1920, and then to Dorothy Stine from 1924 until his death. He had one daughter, Sara, with Radcliffe.
Karloff was a tall man, standing at 6 feet 4 inches (1.93 m). He had a deep, resonant voice which contributed to his success as a horror actor.
He was a respected actor who was admired by his colleagues and fans alike. He is considered one of the greatest horror film actors of all time.
In 1999, Karloff was ranked #20 on the American Film Institute's list of the 50 Greatest American Screen Legends.