Srinivasa Ramanujan was the greatest mathematician in the history of India. He was born in southern India in 1887 and died there in 1920 at the age of 32. He had only one year of college, but his mathematical discoveries, made mostly in isolation, have made him one of 20th and 21st centurys' most influential mathematicians. An account of Ramanujan's life will be presented. Most of Ramanujan's mathematical discoveries were recorded without proofs in notebooks, and a description and history of these notebooks will be provided. A lost notebook of Ramanujan was found in 1976. We shall also give a history and description of the lost notebook. The lecture will conclude with a brief survey of the areas of mathematics to which Ramanujan made profound contributions.