Isaac Mathieu Weill (24 May 1851 – 5 November 1939) was a French mathematician and principal of the Collège Chaptal.

He was educated in the lyceums of Burg and Strasburg, and was admitted to the École Polytechnique in 1870.

[1] Meanwhile, Weill began studies at the military school in Fontainebleau in 1872.

He attained the rank of lieutenant of artillery, but resigned in April 1877.

He was appointed professor of mathematics in 1881, and in October 1898 the school's principal.