Ritchie has decided the time is right to move on, said chairman David Fish.
"It is a company with fantastic brands that are favourites with consumers. I wish the company every success," said Ritchie, who joined UB in 2000.
Also leaving are management services director Bill Winthrop and managing director of northern Europe Mohamed Elsarky, who will be replaced by Anthony Francheterre.
Fish has expanded his role from non-executive to executive chairman. Managing director of UBUK Benoit Testard will run the entire UK operation, taking charge of manufacturing and logistics, in addition to commercial operations.
Chief financial officer Jeff van der Eems will take on the expanded role of chief operating officer and chief financial officer.