The 1909 International Lawn Tennis Challenge was the ninth edition of what is now known as the Davis Cup. For the second straight year, only the British Isles and the United States would challenge Australasia for the Cup. After defeating the British in Philadelphia, the US traveled to Sydney, but was defeated again by the Australasian team. The final was played at the Double Bay Grounds on 27–30 November.

The Davis Cup is the premier international team event in men's tennis. It is run by the International Tennis Federation (ITF) and is contested annually between teams from over 150 competiting countries, making it the world's largest annual team sporting competition. It is described by the organisers as the "World Cup of Tennis", and the winners are referred to as the World Champions. The competition began in 1900 as a challenge between Great Britain and the United States. By 2023, 155 nations entered teams into the competition.