Cornelis Wilhelmus Joannes Maria "Cornelius" Willemse (30 September 1871, Rotterdam - 11 July 1942, Manhattan) was a New York City policeman and detective from 1900 to 1925. He was the author of two memoirs, Behind the Green Lights (1931) and (1933). His books are among the few reliable first-hand accounts of the criminal gangs and police methods of that time.