The historic site in the English Channel, which is capped by a mediaeval monastery, was completely surrounded by sea for 20 minutes at about 9.30pm on Wednesday, when the tidal coefficient, which shows the difference in height between high and low tides, reached 108.
Regional council leader Laurent Beauvais predicted bigger and better tides in the future, notably a 119 coefficient expected in 2015.
The main reason for the mont’s temporary isolation is the demolition of part of a raised road on a dyke that has linked the island to the mainland since 1879.
But silt around it has been reduced by the construction of a dam on the river Couesnon in 2006.
The rest of the road is set to be demolished at the end of 2014 when a new footbridge is finished, leading to the island being cut off between 50 and 90 times a year.
The works have proved controversial due to its cost and to the construction of a car park 2.5 kilometres away from the actual site, sparking a strike of personnel on the tourist attraction.
The Mont Saint Michel has been on the Unesco world heritage list since 1979 and is visited by 2.5 million people per year.