The .577 Nitro Express is a large-bore centerfire rifle cartridge designed for the purpose of hunting large game such as elephant.

The .577 Nitro Express is a straight rimmed .584-inch (14.8 mm) calibre cartridge designed for use in single-shot and double rifles.

It has been made in three case lengths based on their respective black-powder .577 Black Powder Express cartridges.

These large-bore rifles proved very effective against the steel plates used by the Germans, in his book Sniping in France 1914-18 Major H. Hesketh-Prichard, DSO, MC stated that they "pierced them like butter".

[7][8] "Pondoro" Taylor used a Westley Richards .577 Nitro Express double rifle, stating "it did great work for me amongst elephant, rhino and buffalo; it's much too powerful for anything lighter."