Three people have been hurt in the latest run, where competitors are chased by half-ton fighting bulls. It takes place during the nine-day San Fermin festival.
Sky News reported the unnamed Briton, from Nottingham, is in a serious condition in hospital.
The running of the bulls involves six bulls and six steers – gelded bulls – which are released onto the streets to run towards the city’s bullring where they face matadors in a bullfight.
This year, tensions rose in the crowd when one bull was separated from the pack in the final 100 metres and tried to charge runners on all sides.
John Ross, 41, from Manchester, suffered bloodied knees in a fall.
“I managed to run alongside the bull and then fell over,” he said. “Some bloke pulled me under the wooden fence and out of its way.”
It took the animals two minutes and 22 seconds to cover the 850-metre (2,800ft) course.
Fifteen people have died after being gored since records began in 1924.
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