Eugen Langen (1833–1895) was a German entrepreneur, engineer and inventor, involved in the development of the petrol engine and the Wuppertal monorail. In 1857 he worked in his father's sugar factory, JJ Langen & Söhne, after an extensive technical training at the Polytechnic institute in Karlsruhe. Langen met Nikolaus August Otto in 1864. Otto was working on improvements to the gas engine invented by Belgian Etienne Lenoir. The technically trained Langen recognised the potential of Otto's development, and one month after the meeting, founded the first engine factory in the world, NA Otto & Cie.