The Constitution of the Republic of Mauritius does not mention any official language. The Constitution contains one statement in Article 49 that states that "the official language of the Assembly shall be English but any member may address the chair in French" which indicate that French and English are official languages of the National Assembly (parliament) only.
While the lingua franca is Mauritian Creole, French is spoken by a majority of Mauritians and is used in the media while English is used in government and education.