Rugby union, often simply referred to as rugby, is a full contact team sport which originated in England in the early 19th century. One of the two codes of rugby football, it is based on running with the ball in hand. It is played with an oval-shaped ball with a maximum length and width of 30 centimetres (12 in) and 62 centimetres (24 in) respectively. It is played on a field up to 100 metres (330 ft) long and 70 metres (230 ft) wide with H-shaped goal posts on each goal line.

William Webb Ellis is often credited with the invention of running with the ball in hand in 1823 at Rugby School when he allegedly caught the ball while playing football and ran towards the opposition goal. However, the evidence for the story is doubtful. In 1845, the first football laws were written by Rugby School pupils; other significant events in the early development of rugby include the Blackheath Club's decision to leave the Football Association in 1863 and the split between rugby union and rugby league in 1895. Historically an amateur sport, in 1995 the International Rugby Board (IRB) removed restrictions on payments to players, making the game openly professional at the highest level for the first time.

The IRB has been the governing body for rugby union since its formation in 1886. The spread of rugby union grew from the Home Nations of Great Britain and Ireland, and was absorbed by many of the countries associated with the British Empire. Early exponents of the sport included Australia, New Zealand and South Africa. Countries that have adopted rugby union as their de facto national sport include Fiji, Georgia, New Zealand, Samoa, Tonga and Wales. Rugby union is played in over 100 countries across six continents and as of November 2010 118 unions were members of the IRB.