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 A Cop Remembers (1933).
His books are among the few reliable first-hand accounts of the criminal gangs and police methods of that time.