Maximilian Sebastian Janisch is a Swiss PhD in mathematics. He defended his dissertation at the age of 21.
Janisch showed aptitude for mathematics at a very young age and was described as a Wunderkind, or child prodigy. After passing his high school mathematics exams at the age of nine, at the age of twelve, Janisch became the youngest university student in France, and at the age of eighteen, the youngest doctoral student in Switzerland.