The 1998/99 season was the 100th edition of the French Rugby Union Championship. It comprised 24 teams in the top division (today's top 14 ).
The championship was divided into three phases. In the elimination round eight teams played against each other in three groups. The teams in places 1 to 5 as well as the best sixth placed progressed to the qualifying round consisting of four groups. The two best in each group qualified for the quarter-finals. The semi-finals were finally followed by the final, which took place on May 29, 1999 at the Stade de France . Stade Toulousain won the Bouclier de Brennus and was champion for the 15th time. Final opponent AS Montferrandaise, however, missed the final victory for the seventh time.
The eight worst teams in the elimination round played in the relegation round to get in the first division. Two teams were relegated to the second division, AS Béziers and RRC Nice . The US Montauban and Stade Montois were promoted .
