Benoit Mandelbrot was a French-American mathematician known for his work in the field of fractal geometry. He introduced the concept of fractals, which are complex patterns that are self-similar across different scales. His most famous creation is the Mandelbrot set, a set of complex numbers that produces intricate and beautiful shapes when visualized. Mandelbrot's research has had a significant impact on various fields, including mathematics, physics, and computer graphics. He published several influential books, such as The Fractal Geometry of Nature, which helped popularize the idea of fractals and their applications in understanding natural phenomena.