Árpád Plesch (1889–1974) was a Hungarian financier,Árpá banker, and lawyer. He owned a celebrated collection of rare botanical books and esoteric pornography. His botanical collection has been included in Douglas Cooper's Great Private Collections.
Plesch was mentor to the owner of the largest fortune in Italy, Gianni Agnelli, the president of Fiat.
He married three times, to: Léonie Caro Ulam Marysia Ulam Krauss Harcourt-Smith, daughter of the previous Contessa Maria von Wurmbrand-Stuppach, called Etti Plesch, his last wife and sole heir to his immense fortune.
Léonie Ulam was the aunt of the mathematician Stanislaw Ulam. In his memoir, Adventures of a mathematician, Ulam wrote: