While Euclid is believed to be the father of geometry, Pythagoras is called the father of mathematics. He lived in Greece, one and a half hundred years before Euclid.
The contribution of Pythagoras to mathematics is hard to overestimate. In addition to creating his own mathematical school, for the first time in the history of mankind, he made mathematics an applied science, introducing its elements into everyday use.
In addition, Pythagoras had significant input in geometry. All schoolchildren know the Pythagorean theorem, which states that the square of the length of the hypotenuse equals the sum of the squares of the lengths of the legs of the right triangle.
Interesting to know, the great philosopher never wrote anything down, so the story of his life is made up of myths. By the way, not all historians agree that it was Pythagoras who proved his famous trigonometric theorem.