Police said the incident happened as the pedestrian was crossing Broomielaw, near James Watt Street, at about 10:10.
Emergency services attended and the man was taken to the Queen Elizabeth University Hospital. There is no update on his condition.
The westbound bus link lane at the Broomielaw has been closed while police investigate the incident.
A man has been injured after he was struck by a bus while crossing a road in Glasgow city centre.