- Oppolzer, Johann, Ritter von, 1808-18711
- Osler, William, Sir, 1849-19191
- Owen, Richard, 1804-18921
- Paget, George Edward, Sir, 1809-18921
- Pajot, Charles, 1816-18961
- Partridge, Richard, 1805-18731
- Pavy, F. W. (Frederick William), 1829-19111
- Peacock, Thomas B. (Thomas Bevill), 1812-18821
- Pettenkofer, Max von, 1818-19011
- Phillips, John1
- Piorry, P. A. (Pierre Adolphe), 1794-18791
- Playfair, Lyon Playfair, Baron, 1818-18981
- Pollock1
- Priestley, William Overend, Sir, 1829-19001
- Purkyne, Jan Evangelista, 1787-18691
- Quain1
- Radcliffe1
- Ramsbotham, Francis Henry, 1800-18681
- Rayer, Pierre Francois Olive, 1793-18671
- Redwood1