The 30-year-old, whose identity has not been revealed, called his victim "a whore" and "commented on the size of her breasts" in the Paris suburb of Evry last Wednesday.
The 21-year-old woman alerted the bus driver, who jammed his vehicle’s doors and called the police.
Officers then arrested the pervert, and charged him using a new anti-harassment law passed by the French parliament last month.
An investigating source in Paris said: "The aggressor was fast-tracked to court, and on Friday he was sentenced to three months in prison for physical abuse."
The man was also fined the equivalent of about £270 (300 Euros) for "degrading comments" made against the woman, whose identity has also been withheld.