Brooke Magnanti is a forensic scientist and writer, who, until her identity was revealed in November 2009, was known by the pen name Belle de Jour.

While completing her doctoral thesis, in 2003 and 2004, Magnanti worked as a call girl. Her diary, published as the anonymous blog Belle de Jour: Diary of a London Call Girl became popular, as speculation surrounded the identity of Belle de Jour. Magnanti went on to The Intimate Adventures of a London Call Girl in 2005 and The Further Adventures of a London Call Girl in 2006. These were followed by Playing the Game, Belle de Jour's Guide to Men, and Belle's Best Bits.

In 2007, the books were adapted for TV as Secret Diary of a Call Girl, starring Billie Piper. In November 2009, fearing her real identity was about to come out, Magnanti revealed her real name and occupation as a scientist. Her first book published under her real name was the non-fiction The Sex Myth in 2012.

Magnanti's first crime novel, The Turning Tide, will be published by Orion in 2016.