Niels Henrik ABEL was a Norwegian mathematician who made groundbreaking contributions to the field of mathematics. He is best known for his work in the field of algebraic equations, which he solved using the ABEL–Ruffini theorem. He also made significant contributions to the theory of elliptic functions and the development of group theory. ABEL's work has been highly influential in the development of modern mathematics and he is considered one of the greatest mathematicians of all time.