Georges Cantor was a German mathematician born in 1845, best known for founding set theory, which is a fundamental part of modern mathematics. He introduced the concept of different sizes of infinity, demonstrating that some infinities are larger than others. His work laid the groundwork for various mathematical fields, including topology and analysis. Cantor faced significant criticism during his lifetime, but his ideas eventually gained acceptance and transformed mathematical thought. He also developed the Cantor set, a unique and important example in set theory. Cantor passed away in 1918, but his contributions continue to influence mathematics today.