- Ochsner, Edward H. (Edward Herman), 1868-1956, author1
- Ogle, Clairel L. (Clairel Leroy), Jr., 1893- author1
- Oliphant, H. N. (Homer Newton), 1880-1924 author, publisher1
- Osler, William, Sir, 1849-19191
- Ottofy, Louis, 1860- author1
- Overton, Frank, 1867-1
- Pacini, A. J. (August John), 1888- author1
- Palma Molina, JoseĢ Ricardo, 1896- author1
- Parke, Davis & Company, author.1
- Parkes, Louis Coltman, 1857-1942, author1
- Pattee, Alida Frances, author1
- Paul, George P. (George Phillip), 1879- author1
- Pearl, Raymond, 1879-1940, author1
- Peter, Luther C. (Luther Crouse), 1869-1942, author1
- Peters, Fredus Nelson, author1
- Philbrick, Maurice Swain, 1896-1984, author1
- Phillips, Anna C. (Anna Crawford), 1889- author1
- Phillips, Thomas Guthrie, 1887-1
- Pillsbury, Stirling G. (Stirling Gainer), 1898- author1
- Platt, Philip S. (Philip Skinner), 1889- author1