Alphonse Eugène Beau de Rochas (9 April 1815, Digne-les-Bains, Alpes-de-Haute-Provence - 27 March 1893) was a French engineer who originated the principle of the four-stroke internal-combustion engine. His achievement lay partly in his emphasizing the previously unappreciated importance of compressing the fuel–air mixture before ignition. He published his results in 1861, a year after Christian Reithmann was granted a patent in Germany and 16 years before Nicolaus Otto obtained his patent.