The .318 Westley Richards, also known as the .318 Rimless Nitro Express and the .318 Accelerated Express, is a proprietary medium bore centerfire rifle cartridge developed by Westley Richards.

Westley Richards is a British manufacturer of guns and rifles and also a well established gunsmith. The company was founded in 1812 by William Westley Richards, who was responsible for the early innovation of many rifles used in wars featuring the British Army during the 1800s. It remained in the hands of the Richards family until it was purchased by Walter Clode in 1957. Currently the company has two listed directors, Alexander Clode and Sheikh Sultan Bin Jassim Al Thani of Qatar. The company has received a number of royal warrants since 1840.