Madame Alphonsine-Thérèse-Bernardine-Julie de Montgenêt de Saint-Laurent (30 September 1760 in Besançon, France - 8 August 1830 in Paris) was the wife of Baron de Fortisson, a colonel in the French service, and the mistress of Prince Edward, Duke of Kent and Strathearn.
Madame de Saint-Laurent was born 30 September 1760 in Besançon, France to Jean-Claude Mongenêt, a civil engineer, and Jeanne-Claude (Claudine) Pussot and later moved to Quebec.
On the formation of Lower Canada, in August, 1791, Prince Edward, Duke of Kent and Strathearn arrived in Quebec City and shortly afterwards leased Judge Mabane's house for £90 per annum.
He lived at the Duke of Kent House in Quebec City for three years with Madame de Saint Laurent, before he was posted to Halifax, Nova Scotia in 1794.