A mastiff is a type of dog.
Mastiff may also refer to:
Military HMS Mastiff, eight Royal Navy vessels serving between 1797 and 1939 Tadiran Mastiff, a battlefield unmanned aerial vehicle (UAV) built by Tadiran Electronic Industries Mastiff PPV, British Army designation for the Cougar armoured fighting vehicle, with extra armour
Arts and entertainment Mastiff (company), an American video game company Mastiff (novel), a 2011 fantasy novel by Tamora Pierce
Other Mount Mastiff, a mountain in Washington, USA