The Challenger League is the lower league of the Pro League on Rainbow Six Siege, hosted and organized by ESL in association with Ubisoft. The league was introduced at the beginning of Year 2 in order to give teams more exposure and more chances to qualify in Pro League.
The Challenger League was introduced in Year 2 in Europe, North America and Latin America, where teams were divided into two groups in GSL format. Interestingly, the first season in Latin America was not in a GSL group format. The competition was held in Double Elimination format with no grand final.
From Season 8 onwards, the Double Round-Robin format, similar to Pro League, was adopted. In the same year, 2018, Challenger League expanded to Japan, South Korea, Australia and New Zealand, and South East Asia regions.