Pythagoras of Samos was a famous Greek mathematician and philosopher (c. 570 – c. 495 BC). He is known best for the proof of the important Pythagorean theorem, which is about right angle triangles. He started a group of mathematicians, called the Pythagoreans, who worshiped numbers and lived like monks. He had an influence on Plato.

He had a great impact on mathematics, theory of music and astronomy. His theories are still used in mathematics today. He was one of the greatest thinkers of his time.

Pythagoras was born in Samos, a little island off the western coast of Asia Minor. There is not much information about his life. He was said to have had a good childhood. Growing up with two or three brothers, he was well educated. He did not agree with the government and their schooling, so he moved to Croton and set up his own cult (little society) of followers under his rule. His followers did not have any personal possessions, and they were all vegetarians. Pythagoras taught them all, and they had to obey strict rules.

Some say he was the first person to use the term philosophy. Since he worked very closely with his group, the Pythagoreans, it is sometimes hard to tell his works from those of his followers.

Religion was important to the Pythagoreans. They swore their oaths by "1+2+3+4" (which equals 10). They also believed the soul is immortal and goes through a cycle of rebirths until it can become pure. They believed that these souls were in both animal and plant life.