Onocentaur (Latin: onocentaurus, from Ancient Greek: Ονοκένταυροι - Onokéntauroi) is an animal from Medieval bestiaries, similar to the centaur, but part human, part donkey. As with many liminal beings, the onocentaur's nature is one of conflict between its human and animal components.

The first mention by Pythagoras was in the time of rule of Ptolemy II Philadelphus, as quoted by Claudius Aelianus in De Natura Animalium. Aelian as well uses term onokentaura for description of the female form. He interpreted the onocentaur as: "its body resembles that of an ass, its colour is ashen but inclines to white beneath the flanks. It has a human chest with teats and a human face surrounded by thick hair. It may use its arms to seize and hold things but also to run. It has a violent temper and does not endure capture."