Kei Nishikori (錦織 圭, Nishikori Kei?, ; born 29 December 1989) is a Japanese professional tennis player, currently ranked world No. 5 by the Association of Tennis Professionals (ATP). He is the only male Japanese tennis player ever to be ranked inside the top 10 in singles.
He has won 11 singles titles and was runner-up at the 2014 US Open, making him the first male player representing an Asian country to reach a Grand Slam singles final. He also reached the semi-finals at the US Open in 2016. He also became the first man from Asia to qualify for the ATP World Tour Finals and reached the semi-finals in 2014 and 2016. He first reached his career-high singles ranking of world No. 4 in March 2015.