Simon Donaldson is a British mathematician known for his significant contributions to the field of geometry and topology. Born on August 15, 1957, he gained fame for his work on four-manifolds, which are mathematical spaces that have four dimensions. His research has helped to deepen the understanding of complex structures in mathematics. In 1986, Donaldson was awarded the prestigious Fields Medal for his groundbreaking discoveries. He introduced new techniques and concepts, such as Donaldson invariants, which have become essential tools in the study of differential geometry. His work has influenced various areas of mathematics and has applications in theoretical physics as well.