Traitor's Blade is a 2014 swashbuckling novel by Canadian author Sebastien de Castell. It is the first book in de Castell's "Greatcoats" series, which follows the adventures and misfortunes of the titular Greatcoats, the remnants of an ancient order of travelling magistrates and duelists. The second book, titled Knight's Shadow, was published later in 2014, while the third, titled Saint's Blood, was released in 2016. The fourth book, Tyrant's Throne, was released in 2017.