The monarch, who is 52 years old, was in “close contact” with the Covid-positive person on Sunday, a palace source said. The contact, who has not been identified, then tested positive on Monday.
In a statement, the palace said that other members of the royal family, including Queen Letizia and the king’s two daughters, “may continue their activities normally”.
King Felipe will isolate himself for 10 days starting from Monday, the palace said, “in conformity with health rules”.
It comes after 15-year-old Princess Leonor, who is heir to the throne, underwent a 14-day self-isolation period in September after someone tested positive in her classroom. She tested negative after her period of isolation.
The news about Felipe VI comes as Spain has recorded more than 1.6 million infections and 43,131 deaths from Covid-19 so far. The country is the second worst-hit in western Europe, in terms of confirmed cases, after France.
Though the country has recorded a decline in per million cases, the overall number of infections has grown by almost 26,000 since Friday, while the number of deaths increased by 512 over the weekend, the health ministry said.
The country recorded less than 400 Covid-19 cases per 100,000 people over the last 14 days as compared to almost 530 cases at the start of November.
The Spanish government is planning a comprehensive vaccine programme in January, with the establishment of 13,000 vaccination centres announced by prime minister Pedro Sanchez during the virtual G20 summit on Sunday. Mr Sanchez said he expects a substantial proportion of the population to be vaccinated in the first six months of 2021.