Josef Ofner (Austrian, born 1868) Sandor Oláh (Hungarian, 1886–1966) Joseph Maria Olbrich (German, 1867–1908) Georges Omerth (French, active ca. 1895–1925) Karel Opatrny (Czech, 1881–1961) Gustav Oppel (German, 1891–1978) Gyula Oppenlander (Hungarian) Kristin Öqvist (Swedish, born 1983) Emmanuel-Joseph Orazi (French, 1860–1934) Carl Ostersetzer (German, 1850–1914) Carl Osterzetzer H. Othlinghaus (German, XX) Fernand Ouillon-Carrère (French) Willard Dryden Paddock (American, 1873–1956) Arnost Paderlik (Czech, 1919–1999)
Kalman Padua (Hungarian, 1885–1958) Oskar Pafka (Czech, 1896–1949) Charles Paillet (French, 1871–1937) Zoltán Páldy (Hungarian, born 1884) Zsigmond Palnagy (Hungarian, 1896–1949) K. Pap (Czech, XX) Eric Pape (American, 1870–1938) Zoltan Papp (Hungarian, born 1924) Vicente García de Paredes (Spanish, 1845–1903) Roland Paris (German, 1894–1945) Einar Parslev (Danish, 1891–1977) Edith Barretto Stevens Parsons (American, 1878–1956) Jenö Pászk (Hungarian, 1895–1948) Mihaly Patay (Hungarian, 1910–1956) Károly Patkó (Hungarian, 1895–1941)
