László Beleznai (November 16,ászló 1891 in Budapest – March 23, 1953 in Budapest) was a Hungarian water polo player and freestyle swimmer who competed in the 1912 Summer Olympics. He was a member of the Hungarian water polo team, which competed in the 1912 tournament.
Also he was a member of the Hungarian 4x200 metre freestyle relay team, which qualified for the final, but did not compete. In the 100 metre freestyle event he qualified for the quarterfinals, but did also not compete.