| 1984 Five Nations Championship | |
| Date: | 21 January - 17 March 1984 |
| Countries: | |
| Count: | 12 |
| Grand Slam: | (2nd title) |
| Triple Crown: | (9th title) |
| Matches: | 10 |
| Tries: | 27 |
| Top Point Scorer: |  Jean-Patrick Lescarboura (54 points) |
| Top Try Scorer: | Philippe Sella (3 tries) |
| Previous Year: | 1983 |
| Previous Tournament: | 1983 Five Nations Championship |
| Next Year: | 1985 |
| Next Tournament: | 1985 Five Nations Championship |
The 1984 Five Nations Championship was the fifty-fifth series of the rugby union Five Nations Championship. Including the previous incarnations as the Home Nations and Five Nations, this was the ninetieth series of the northern hemisphere rugby union championship. Ten matches were played between 21 January and 17 March.
Scotland won the championship outright for the first time since 1938. It was their twelfth outright championship, excluding a further seven shared titles. Their four wins gave them the Grand Slam for the first time since 1925 and the second in all, and the Triple Crown for the ninth time and the first since 1938.
It was also the second occasion, after 1978, in which two teams each with three victories faced off against each other in the final round of matches, with both capable of completing a Grand Slam with a victory.
The teams involved were:
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