The Comoros international moves to The City Ground from Swedish top-flight side Malmo.
Bachirou started his career at Paris Saint-Germain before moving to Scottish side Greenock Morton, making over 140 appearances ahead of joining Swedish side Ostersunds.
During his time with Graham Potter’s side, he lifted the Swedish Cup in 2016-17, and was a runner-up in the following campaign, before switching to Malmo in 2018.
The midfielder has extensive experience of both the Champions League and the Europa League during his time in Sweden, helping Ostersunds reach the Europa League round of 32 in 2017, while reaching the same stage of the competition with Malmo in the past two seasons.
The 30-year-old now moves to The City Ground where he teams up with Sabri Lamouchi’s Reds ahead of the 2020-21 campaign.