Jenő Keményffy was a Hungarian painter. His brothers-in-law were József Vészi and József Róna. Niece Margit Vészi.

Son of Gábor Ádám Keményffy (1832-1899), grain merchant and stock exchange secretary, and Nina Schossberger (1844-1915). He was a pupil of Bertalan Székely and Gyula Aggházy at the Budapest School of Drawing, then attended the private school of Simon Hollósy in Munich. In 1898 he worked at the painting school in Nagybánya. From 1899 onwards he exhibited naturalistic life pictures, cityscapes and still lifes, also at the Kunsthalle in Budapest. In 1912 he was awarded the Prize of the Lipótváros Casino. Two of his works were acquired by the Hungarian National Gallery and his self-portrait by the Ernst Museum. In 1908 he converted to Unitarianism. His death was caused by pneumonia.

His wife was Hedvig Kertész, daughter of Bernát Kertész and Emma Langsfeld, whom he married on 24 March 1901 in Terézváros, Budapest. They divorced in 1919.