Almasa Royal Palace will be rebranded in phases to become The St Regis Almasa by Spring 2020, remaining open to guests throughout the transition period.
It has 434 rooms, including 270 rooms, 90 suites, 60 apartments and 14 villas, alongside outdoor and indoor swimming pools, a gym, spa, club house and numerous food and drink outlets.
The property is adjacent to a 42,000 square-foot centre which hosts conventions, events and official visits in an area the government has slated to become the New Administrative Capital city.
Marriott will be working with the National Authority for Management and Investment on the project.