John Robert Isner (born April 26, 1985) is an American professional tennis player. He achieved his career-high rank of No. 18 on July 5, 2010, and has been as high as the second-ranked American tennis player behind Andy Roddick. His most famous victories were against Roddick in the 2009 US Open, and against Nicolas Mahut at the 2010 Wimbledon Championships where he played the longest ever professional tennis match, which lasted 11 hours and 5 minutes over the course of three days.
Isner played collegiate tennis at the University of Georgia from 2004 to 2007 and became the school's all-time leader in singles and doubles victories, earning All-American honors each of his four years and leading Georgia to the 2007 NCAA championship.
Isner began his professional career in earnest in the summer of 2007. With a world ranking of No. 839, he needed wild card entries into the main draws of every tournament, even at the Futures level.