Artists: O
- Obregon, Alejandro
- Odenbach, Marcel
- Oelman, Michael
- Ofili, Chris
- Olbrich, Joseph Maria
- Oldenburg, Claes
- Olitski, Jules
- Oliveira, Nathan
- Oliver, Isaac
- Oliver, Madge
- Olsen, John
- Onley, Toni
- Ono, Yoko
- Onslow-Ford, Gordon
- Opie, Julian
- Opie, John
- Oppenheim, Dennis
- Opsomer, Isidore
- Orchardson, Sir William Quiller
- Organ, Bryan
- Orkin, Ruth
- Orozco, José Clemente
- Orozco, Gabriel
- Orpen, Sir William
- Orr, Chris
- Ortman, George
- Osborne, Walter Frederick
- Ospovat, Henry
- Östberg, Ragnar
- Otero, Alejandro
- Otreba, Ryszard
- Ottley, William Young
- Ouless, Walter William
- Oulton, Thérčse
- Oursler, Tony
- Outcault, Richard Felton
- Ovenden, Graham
- Owen, William
- Owen, Samuel
- Owen, Edward Pryce
- Ozbek, Rifat
- Ozenfant, Amédée