The Britons killed were travelling in a taxi which was overcome by floodwater, The Telegraph reports.
The Spanish weather forecasters said 8in of rain fell in four hours.
Their vehicle was swept away by a torrent of water near the coastal resort of S'Illot.
At least ten people have died and it's thought that one child is still missing following a series of devastating floods which swept across the holiday island of Mallorca, in Spain's Balearic Islands.
Soldiers used shovels to clear the thick mud from the streets of the town, 60 kilometres (40 miles) east of the island's capital of Palma.
Piles of rubbish and wrecked furniture cluttered the streets in Sant Llorenc des Cardassar, one of the worst-hit villages, while locals with the aid of volunteers used mops to clean up the water flooding their homes.
"It all happened in less than 10 minutes", one told Spanish TV.
A Foreign Office spokesman said: "We are supporting the family of two British people following their deaths in Spain, and will do all we can to assist them at this deeply hard time".
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According to Diario de Mallorca, the bodies of an 81-year-old man and 83-year-old woman were among the first to be found on Tuesday.
Other victims were found in Arta and the coastal town of S'illot, where the overflowed creek reaches the sea.
Former municipal mayor Rafel Gili Sastre, 71 was later found dead at his home, the paper said.
He said: "My solidarity and support goes out to the families and friends of victims and all the affected by these tragic floods", he said.
The regional government called an emergency meeting and authorities said rescue workers and military units were heading to the area to help.
Spain's Prime Minister, Pedro Sanchez, visited the disaster zone yesterday while tennis star Rafa Nadal rolled up his sleeves helped in the massive clean-up operation.
Earlier on Wednesday, Nadal said on Instagram he was offering to open up his sports centre and tennis academy to people made homeless by the floods.