The team won five French top-division championships in 1949, 1950, 1993 (in a match decided by an irregular try accorded by the referee),[1] 2013, and 2018 as well as one Coupe de France in 1948.

In 1898 several alumni of Castres' municipal college met in a city centre bar and decided to create a team allowing them to play their favourite sport, rugby union.

It was decided that this club would be named Castres Olympique and its colours would be changed from yellow and black to its current blue, white and grey.

[4][5] Jacques Fouroux, being already suspicious before the match of the referee, saw in this outcome a conspiracy of his enemies from inside the rugby union French Federation.

After finishing first in the 2021-2022 Top 14, Castres played a semi-final against the Stade Toulousain of Antoine Dupont and Romain Ntamack, beating them 24–18.

The Castres squad for the 2024–25 season is:[11][12] Note: Flags indicate national union under World Rugby eligibility rules.