Lionel Atwill (1 March 1885 – 22 April 1946) was an English stage and film actor born in Croydon, London, England.

He studied architecture before his stage debut at the Garrick Theatre, London in 1904. He become a star in Broadway theatre by 1918, and made his screen debut in 1919. He acted on the stage in Australia but was most famous for his U.S. horror roles in the 1930s. His two most memorable parts were as the crazed, disfigured sculptor in Mystery of the Wax Museum (Warner Brothers, 1933), and as Inspector Krogh in Son of Frankenstein (1939), memorably sent up by Kenneth Mars in Mel Brooks's Young Frankenstein (1974).

When he was not cast in macabre roles, Atwill often appeared in the 1930s as righteous-minded authority figures. For example, in 1937's less memorable The Wrong Road for RKO, investigator Atwill persuades a young, bank-robbing ingenue played by Helen Mack and her boyfriend Richard Cromwell to return their ill-gotten $100,000 and give up a life of crime. Two of Atwill's other notable non-horror roles were opposite his contemporary Basil Rathbone in films featuring Arthur Conan Doyle's character Sherlock Holmes, including a role as Dr. James Mortimer in 20th Century Fox's 1939 film rendition of the Conan Doyle novel The Hound of the Baskervilles, and the 1943 Universal Studios film Sherlock Holmes and the Secret Weapon, in which he played Holmes' archenemy and super-villain, Professor Moriarty.

Atwill remained a stalwart of the Universal horror films until his career flagged in the 1940s because of a widely publicized sex scandal in 1941, during the investigation of which he was charged in 1942 with perjury at a trial in which Atwill had been accused of staging a sex orgy at his home.

He died while working on the 1946 film serial Lost City of the Jungle. His ashes were once inurned in Chapel of the Pines Crematory.Lionel Atwill, licensed under CC-BY-SA, full list of contributors on Wikipedia