What was the name of the spanish officer who crossed the Isthmus of Panama to reach the Pacific Ocean in 1513?

His name was Vasco Núñez de Balboa. He was the first explorer one to cross into and see the Pacific Ocean. He, however, was not the one who named it. After him, Ferdinand Magellan -- who captained the first circumnavigatin of the globe -- traveled through the Pacific and named it then in 1520.