Todd, who has led the companies for the last three years, will depart following the brands transitioning to the mainstream Tui group.
She will be replaced by Tui’s head of Ireland, Chris Logan on September 30.
Logan, who joined the group in 2009, has been in his current role since February 2015 overseeing the Falcon, Thomson and First Choice brands.
Prior to that, he was general manager for groups and weddings between 2009-2010 and later head of property and portfolio change.
He is now due to take over the Crystal Ski and Thomson Lakes & Mountains brands which are being retained by Tui after the group put the rest of its specialist division up for sale.
Renamed Travelopia; the portfolio features more than 50 brands and is currently up for sale in a process expected to be finalised during the first quarter of next year.
Commercial director of Tui UK and Ireland Andrew Flintham, said: “I would like to thank Tamsin Todd for her hard work and dedication over the last three years and would like to take this opportunity to wish her every success in the future.
"Tamsin has been integral to the smooth transition of Crystal Ski into Tui UK and Ireland. It would have been much more challenging without her great support to both the project team and our Crystal colleagues.”