Mourinho, who replaced Louis van Gaal at United this summer, clashed regularly with Manuel Pellegrini's successor Guardiola while in Spain and they will go head-to-head immediately after the first international break of the season, with the return game at the Etihad on February 25, 2017.
Champions Leicester begin their defence at promoted Hull City on August 13, while Mourinho takes his team to Bournemouth and Guardiola's City host Sunderland.