Petro Evstaf'evic Stojan (Russian: ???? ??????????? ?????, also known by the pseudonyms Ribaulb, Radovich and Šulerc) (June 22, 1884 in Izmail, Bessarabia — May 3, 1961 in Nice) was a Ukrainian esperantist, bibliographer and lexicographer and a member of the Esperanto Language Committee (Lingva Komitato) from 1914.