The open-top double-decker bus, which belonged to the company Big Bus Tours crashed in the tunnel underneath the Alexandre III bridge, leaving four injured, one of them seriously.
The bus that was carrying around 20 passengers, crashed into the bridge, a tourist hotspot due to its ornate structure and views over the Eiffel Tower and River Seine.
Images posted on Twitter showed damage to the top deck of the bus which appears to have been too high to pass through the tunnel.
It was not clear whether the injured passengers were on the top deck of the bus at the time of the crash.
Paris : le bus de tourisme s'encastre dans le tunnel, un blessé grave https://t.co/fUImPmiRfS— Le Parisien | Paris (@LeParisien_75) June 23, 2017
Numerous emergency vehicles were stationed nearby and the road was closed off to traffic after the accident which occurred around 1pm and on a day when Paris was hosting a large-scale event on the Seine river to promote the city's 2024 Olympics bid, including a floating track.
The bus had deviated from the usual route around the capital to go under the tunnel, which is normally forbidden for vehicles higher than 2.7 metres, according to the Parisian newspaper.
A police source told AFP the bus had been diverted because of the Olympics event.
The Big Bus Tours company, which offers sightseeing trips around Paris on open-top buses, confirmed to AFP that one of its vehicles had been involved in the accident, without giving further details.
URGENT PARIS - 4 blessés dont 1 grave dans un accident de bus de tourisme à étages sous le pont Alexandre III à Paris (images BFM) pic.twitter.com/lqXjAv85q1— ALERTES INFO (@ALERTES_INFO) June 23, 2017
Map: Google Maps