The 1891 British Isles tour to South Africa was the first British Isles rugby union tour of South Africa and only the second overseas tour conducted by a joint British team. Between 9 July and 7 September, the team played 20 games, including three Tests against the South Africa national rugby union team. The British Isles not only won all three Test matches, but also won all 17 provincial games. Although not named as such at the time, the tour is retrospectively recognised as a British Lions tour.

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.