The 1904 British Isles tour to New Zealand and Australia was the sixth tour by a British Isles rugby union team and the third to New Zealand or Australia. It is retrospectively classed as one of the British Lions tours, as the Lions naming convention was not adopted until 1950.

The British & Irish Lions is a rugby union team selected from players eligible for the national teams of England, Ireland, Scotland, and Wales. The Lions are a test side and most often select players who have already played for their national team, although they can pick uncapped players who are eligible for any of the four unions. The team tours every four years, with these rotating between Australia, New Zealand and South Africa in order. The most recent test series, the 2021 series against South Africa, was won 2–1 by South Africa.