Underbelly: Razor, the fourth series of the Australian Nine Network crime drama anthology series Underbelly, originally aired from 21 August 2011 to 6 November 2011. It is a thirteen-part series detailing real events that occurred in Sydney between 1927 and 1936. The series depicts the "razor gangs" who controlled the city's underworld during the era and the violent war between the two "vice queen" powers, Tilly Devine and Kate Leigh. It is also the last season in the Underbelly franchise that contains 13 episodes. In contrast to the previous Underbelly instalments, which were based on books by John Silvester and Andrew Rule, Razor is based on the Ned Kelly Award-winning book of the same name, written by Larry Writer.