Adrien-Marie Legendre, French mathematician and theorist (died 1833)

Adrien-Marie Legendre was a French mathematician who made numerous contributions to mathematics. Well-known and important concepts such as the Legendre polynomials and Legendre transformation are named after him. He is also known for his contributions to the method of least squares, and was the first to officially publish on it, though Carl Friedrich Gauss had discovered it before him.

September 18 is the 261st day of the year in the Gregorian calendar; 104 days remain until the end of the year.