- "With Operation Chimera, we are exploring a new fantasy: quarantine and biohazard. The two operators are biohazard specialists from France and Russia. During this first Season, our first major coop event, Outbreak, will take place over four weeks."
— Official Website Description
Operation Chimera was the eighth free expansion of Tom Clancy's Rainbow Six Siege, and the first expansion of Year Three. It added two new Operators from Team Rainbow's newfound CBRN Threat Unit and a limited-time event called Outbreak, which ended on April 4, 2018.
It was officially announced on November 19, 2017, and released on March 6, 2018 for Season Pass owners.
- Outbreak (Limited Time, removed on April 4, 2018)
- Due to backlash surrounding a number of controversial changes, Ubisoft did a give away of Ash's Sidewinder Elite Uniform upon the season's release to those who played the game between the announcement made on January 26th, 2018 and its release date.
- Due to a deployment issue, the Sidewinder Elite Uniform was unable to be released properly for everyone on the day and had been temporarily removed until it was eventually fixed.