John Isner is an American professional tennis player known for his powerful serve and tall stature, standing at 6 feet 10 inches. He turned professional in 2007 and has since become one of the top players in the world, achieving a career-high ATP singles ranking of No. 8 in 2018. Isner gained fame for his performance in Grand Slam tournaments, particularly at Wimbledon, where he played in the longest match in tennis history against Nicholas Mahut in 2010. He has also represented the United States in the Davis Cup and has won multiple ATP titles throughout his career.