William Sharpe is an American economist and a professor emeritus at Stanford University. He is best known for developing the Sharpe Ratio, a measure used to evaluate the risk-adjusted return of an investment. His work has significantly influenced modern finance and investment strategies. In 1990, Sharpe was awarded the Nobel Prize in Economic Sciences for his contributions to the field, particularly in portfolio theory. His research has helped investors understand how to optimize their portfolios by balancing risk and return, making him a key figure in the development of financial economics.