Ōsensei

Ōsensei (大先生/翁先生) is a Japanese term, a stronger form of sensei (先生).

Ōsensei may also refer to:
 * Morihei Ueshiba (1883–1969), founder of Aikido
 * Masutatsu Oyama (1923–1994), founder of Kyokushinkai karate
 * O-Sensei, a fictional character in the DC Universe