LISBON — How the roles have reversed: The colonizer, some Portuguese contend, has been colonized.

On the Portuguese coast of Cascais, where the nation’s royal court used to summer, a new 14-story condominium building looms confidently by the sea. So many of its apartments have been bought by Angola’s ruling class — sometimes a handful at a time — that the development has a nickname: the “Angolans’ building.”

Along the grandest shopping boulevard in the capital, Lisbon, Angola’s elite buy designer suits and handbags by the armful. And on one corner, above Louis Vuitton, sits the local office of Africa’s richest woman, Isabel dos Santos, a billionaire from Angola who has become one of Portugal’s most powerful figures by buying large chunks of the country’s banking, media and energy industries.

The money flowing into Portugal comes from the colony it dominated, often brutally, for hundreds of years, Angola. Now, the African nation is a major oil producer that has been led for the last 38 years by Ms. dos Santos’s father, President José Eduardo dos Santos.

Angola’s ruling class has profited so much during his tenure — and channeled so much of that money into Portugal — that when Angola threatened to cut off ties in recent years in response to reports that Angolan officials were being investigated for corruption in Portugal, Portugal’s foreign minister promptly apologized, setting off an intercontinental debate about the changing power dynamics between the nations.