Which singer was known as Ol' Blue Eyes?

Francis Albert Sinatra was an American singer and actor. Nicknamed the "Chairman of the Board" and later called "Ol' Blue Eyes", Sinatra was one of the most popular entertainers of the 1940s, 1950s, and 1960s. He is among the world's best-selling music artists with an estimated 150 million record sales. Sinatra released his debut album, The Voice of Frank Sinatra, in 1946. Born to Italian immigrants in Hoboken, New Jersey, Sinatra was greatly influenced by the intimate, easy-listening vocal style of Bing Crosby and began his musical career in the swing era with bandleaders Harry James and Tommy Dorsey.

Source: Wikipedia