1978 Five Nations Championship

The 1978 Five Nations Championship was the forty-ninth series of the rugby union Five Nations Championship. Including the previous incarnations as the Home Nations and Five Nations, this was the eighty-fourth series of the northern hemisphere rugby union championship. Ten matches were played between 21 January and 18 March. The tournament was contested by England, France, Ireland, Scotland, and Wales. The championship was won by Wales, the twentieth time the team won the competition outright. The Welsh had won another nine titles, which were shared with other teams. Having won all four of their games, Wales also won the Grand Slam, a record eighth occasion the team did so - Wales had formerly shared the record of seven with England. Victories over England, Ireland and Scotland (the Home Nations), also meant Wales won the Triple Crown for the third consecutive time, a record, given no other team had ever won the Triple Crown more than twice in a row. It was Wales' fifteenth in total, also a record, surpassing the fourteen won by England.

It was also the first ever occasion on which two teams each with 3 victories faced off against each other in the final round of matches, with both capable of completing a Grand Slam with a victory.