Jean-Victor Poncelet is often called the founder of projective geometry. He was born in Metz, France, and made a number of important contributions to geometry during his lifetime.
As a young man he was taught by Monge, and took part in the Napoleonic campaign in Russia as a lieutenant engineer. After a particularly difficult battle he was left for dead, and captured and imprisoned by the Russians for two years in 1813.
Whilst a prisoner of war, he studied geometry, noting down his discoveries, which he then published in 1822 in a book called Applications of Analysis and Geometry. This was merely an introduction to his most important work, Treatise on the Projective Properties of Figures. This describe the principle of continuity, which was highly controversial for the time, as it led to the introduction of imaginary points.
Poncelet returned to France in 1814, where he worked as a military engineer, then taught mechanics at a local military school. During this period he applied mathematical principles to real life problems, including the waterwheel, and the first inward-flow turbine (although it was not built for some years).
Not much is known of his later life, but that he died in France in 1867.