The 1999 U.S. Open Champion was Andre Agassi, a professional tennis player from the United States. He won eight Grand Slam singles titles during his career and was one of the most successful players of the 1990s. Agassi was the first male player to win all four Grand Slam singles titles, and he was the only player to have won the Career Grand Slam on three different surfaces. He was also the first male player to win the U.S. Open and the Australian Open in the same year.