Alphonse Eugène Beau de Rochas (9 April 1815, Digne-les-Bains, Alpes-de-Haute-Provence – 27 March 1893, Vincennes) was a French engineer.

He was the first to patent the four-stroke engine in 1862, but he did not build one and the idea was subsequently developed by Nicolaus Otto and other engineers.

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