The FTSE 100-listed firm said Thomas will take over as its chairman when Tim Stevenson retires after seven years in the role at the end of the group's Annual General Meeting on 26 July 2018.
The specialty chemicals group noted that Thomas has been chief executive officer and chairman of Covestro since 2015 and will step down from those roles at the end of May 2018.
He was chief executive officer at Covestro's predecessor, Bayer MaterialScience, prior to its demerger from Bayer AG. Thomas also spent five years at Huntsman Corporation (NYSE:HUN) including as president of its Polyurethanes, Performance and Advanced Materials divisions.
Commenting on the appointment of successor, Tim Stevenson, said: “I am confident that he will successfully steer Johnson Matthey to deliver continued value for our shareholders as we pursue our vision to make the world a cleaner and healthier place.”
In mid-morning trading, Johnson Matthey's shares were up 0.9% at 3,331.0p.