A disappointing start to the season for Gasly has seen the Frenchman comprehensively beaten by Verstappen, who has scored nearly three times as many points as his team-mate.
His progress has been accelerated as a result of Gasly's flagging fortunes, as he makes the mid-season switch in much the way Verstappen did when he replaced Kvyat in 2016.
“The Team will use the next nine races to evaluate Alex's performance in order to make an informed decision as to who will drive alongside Max in 2020.”
Albon took to social media where he described the mid-season change as ‘surreal'.
“Surreal to have been given this massive opportunity,” he wrote.
“Can't thank you enough for believing in me and making this possible. It's a big jump into the deep end, but I've got my swimming shorts on!
“Thanks to all the guys at @ToroRosso, especially Franz Tost for the massive opportunity in F1 and never-ending support throughout my first year! Now to focus for my first race with the team in Spa.”
In his 12 grand prix starts Albon has recorded five top 10 finishes, with a best result of sixth coming at the German Grand Prix.
His first race with his new team will be at Belgium's Spa-Francorchamps circuit, which will be held over the August 30 – September 1 weekend.