Joyeuse was the name of Charlemagne’s personal sword. The name translates as ‘joyful’.
A sword identified with Charlemagne’s Joyeuse was carried in front of the coronation processionals for French kings, for the first time in 1270 at the coronation of Philip III, and for the last time in 1824 at the coronation of Charles X. The sword was kept in the Saint Denis Basilica since at least 1505, and it was moved to the Louvre in 1793.
The 11th century Song of Roland describes the sword:
[Charlemagne] was wearing his fine white coat of mail and his helmet with gold-studded stones; by his side hung Joyeuse, and never was there a sword to match it; its colour changed thirty times a day.