Nicholas Hilmy Kyrgios ( KIRR-ee-oss; born 27 April 1995) is an Australian professional tennis player who is currently ranked world no. 19 in men's singles by the Association of Tennis Professionals (ATP). He is currently the highest-ranked Australian in the ATP rankings. Kyrgios has won four ATP Titles, and has reached seven ATP finals, including the 2017 Cincinnati Masters.

During his junior career, Kyrgios won the boys' singles event at the 2013 Australian Open and the boys' doubles event at the 2013 Wimbledon Championships. During his professional career, Kyrgios reached the quarter-finals of the 2014 Wimbledon Championships"upsetting then world no. 1 Rafael Nadal and world no. 13 Richard Gasquet en route"and the quarter-finals of the 2015 Australian Open. Kyrgios is only the second player, after fellow Australian Lleyton Hewitt, to have beaten Roger Federer, Rafael Nadal and Novak Djokovic in their first meetings.

During much of his career, Kyrgios has been met with a negative reception. He has been accused of "tanking", verbal abuse and unsportsmanlike conduct by much of the media and former tennis players including John McEnroe. Other tennis players, however, including John Lloyd, have praised Kyrgios's unique style, character and flair, and in 2018 his renewed focus at the 2018 Australian Open attracted much media attention.