The 1999–2000 French Rugby Union Championship was played by 24 teams divided in the preliminary phase in two pool of 12. The first two team of each pool were directly admitted to the quarter finals. The team classified from 3rd to 6th of each pool were admitted to a Barrage round. The four winners were admitted also to the quarter of finals.
Stade Français won the title beating in the final the Colomiers (at the first final of their history). It was the second victory for the Stade Français in the professional era.
Ath the end of the season four team were relegated to lower division: Montauban, Toulon, Racing Paris, Nîmes. There was only one promotion from second division, (Béziers), in order to reduce to 21 the number of clubs in first division in 1999–2000, and 16 in the 2000–01 season.