Police and ambulance crews were called to the scene at the Bay Horse Inn at Bentley at 9.20pm.
A South Yorkshire Police spokesman said: "Police responded to reports of people fighting at the location.
"A man was taken to Doncaster Royal infirmary for treatment.
"The extent or nature of his injuries are not known at this time.
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"An investigation into the incident is ongoing."
Police cordoned off the area last night and the area was still understood to be sealed off this morning.
No arrests have been made yet.
Ring police with information on 101.
We contacted the pub for comment and are awaiting a reply.