Mont-Saint-Aignan (French pronunciation: [mɔ̃ sɛ̃t‿ɛɲɑ̃]) is a commune in the Seine-Maritime department in the region of Normandy, northwestern France.

[3] Due to the presence of higher education institutions (notably the University of Rouen and the NEOMA Business School) and the city's relatively small population, Mont-Saint-Aignan is considered the French city that has the largest proportion of students relative to its population (students represented in 2014 25,61% of the total population).

The town is ultimately named for the ancient Saint Aignan of Orleans.

The parishes of Saint-Aignan (Latin: Sanctus Anianus) and Mont-aux-Malades (Monte Infirmorum, which takes its name from a hospital) are mentioned in documents dating back to the 12th century.

Henry II built a church there dedicated to Thomas Becket in 1176 in an attempt to make up for his unwitting role in the murder of the Archbishop of Canterbury.