The Tenderloin was a once-seedy neighborhood in the heart of the New York City borough of Manhattan. Police Captain Alexander Williams allegedly coined the term in the late 1870s. This district was in Midtown Manhattan from 23rd Street to 42nd Street and Fifth Avenue to Seventh Avenue, much of which is known now as Chelsea and the Garment district. The northwest corner of the Tenderloin was Longacre Square, now called Times Square.
The Tenderloin was a notorious red-light district. The raffish reputation of the Tenderloin's 1890s bordellos, repeatedly raided by Anthony Comstock's vice squad, was recreated in the 1960 Sheldon Harnick-Jerry Bock musical Tenderloin, based on a novel by Samuel Hopkins Adams.
The Tenderloin of the early 20th Century is described from a police perspective in Behind the Green Lights, the memoirs of Police Captain Cornelius Willemse.
The name appears to have fallen out of favor in the 1940s, when massive redevelopment of the area removed much of the associated stigma.