Diophantus of Alexandria (circa 200/214 - circa 284/298) was an ancient Greek mathematician.
We do not know much of his life. It is just known that he lived in Alexandria and he died 84 years old. Probably Diophantus was Hellenized Babylonian.
He was known for his study of equations with variables which take on rational valuess and these Diophantine equations are named after him. Diophantus is sometimes known as the "father of Algebra".
It was in the margin of a French translation of Diophantus' work Aritmetike (The Arithmetic) from circa 250 that Pierre de Fermat wrote his famous comment that is known as Fermat's last theorem.
Diophantus also wrote a treatise about polygonal numbers.