Hanna informed the group he did not intend to seek re-election at its next annual general meeting in 2024 due to personal reasons.
The board said it would be initiating “a comprehensive search process” to find a new chairman and would share updates when appropriate.
Additionally, TRG stated Hanna would remain in his role as TRG chairman until his successor has been appointed in order to allow for an “orderly handover”.
Hanna said: "It has been a privilege to work at TRG and I will be leaving the company in great shape with the business trading really strongly, outperforming the market and making good progress on its strategic options.
“I would like to thank the board and management team as well as our brilliant colleagues across the business for their great work and support during my time with TRG. I wish them and the group much continued success."
This comes as TRG reported a 10% increase in total revenue in the 26 weeks to 2 July this year, rising from £423.4m to £467.4m, attributed to “standout performances” across its pub and concession divisions.
Within its pub estate, which includes Brunning & Price, the group saw an 8% like-for-like increase while its other ventures, namely Wagamama and concessions trade, benefited from a 7% and 29% upswing respectively.
TRG CEO Andy Hornby said: "On behalf of the board I would like to thank Hanna for his outstanding contribution to the business.
“He has been an exceptional chairman and a hugely valued colleague during a critically important period for TRG as we have successfully recovered from the covid pandemic and made good progress with our strategy.
“Hanna’s leadership of the board will be greatly missed by all his colleagues at TRG and we wish him well."