Maurice Fernez (30 August 1885 – 31 January 1952) was a French inventor and pioneer in the field of underwater breathing apparatus, respirators and gas masks. He was pivotal in the transition of diving from the tethered diving helmet and suit of the nineteenth century to the free diving with self-contained equipment of the twentieth century. All Fernez invented apparatus were surface-supplied but his inventions, especially his mouthpiece equipped with a one-way valve, inspired the scuba diving pioneer Yves le Prieur. He was also a talented businessman who created a company to manufacture and sell the breathing apparatus he invented, and expanded its range of products to include gas masks, respirators and filters.