|Place of origin||France|
|Main ingredients||Béchamel sauce, Gruyère|
A Mornay sauce is a béchamel sauce with shredded or grated Gruyère cheese added.   Some variations use different combinations of Gruyère, Emmental cheese, or white Cheddar.  A Mornay sauce made with cheddar is commonly used to make macaroni and cheese.
The name origin of Mornay sauce is debated. It may be named after Philippe, duc de Mornay (1549–1623), Governor of Saumur and seigneur du Plessis-Marly, writer and diplomat, but a cheese sauce during this time would have to have been based on a velouté sauce, for Béchamel had not yet been developed. 
Sauce Mornay does not appear in Le cuisinier Royal, 10th edition, 1820. Perhaps sauce Mornay is not older than the great Parisian restaurant of the 19th century, Le Grand Véfour in the arcades of the Palais-Royal, where sauce Mornay was introduced. 
In the Tout-Paris of Charles X, the Mornay name was represented by two stylish men, the marquis de Mornay and his brother, styled comte Charles. They figure in Lady Blessington's memoir of a stay in Paris in 1828–29, The Idler in France.  They might also be considered, when an eponym is sought for sauce Mornay.
- La Technique. New York, NY 10013: The French Culinary Institute. 1995. p. 44.
- Hasterosk, edição de Aude Mantoux ; colaboração de Laurence Alvado e Rupert (2007). Le grande Larousse gastronomique ([Éd. 2007]. ed.). Paris: Larousse. p. 783. ISBN 978-2-03-582360-1.
- McGee, Harold (2004). On Food and Cooking; The Science and Lore of the Kitchen. New York, NY, USA: Scribner. pp. 65–66 and 587. ISBN 0-684-80001-2.
- "Cuisine Bourgeoise". History of Gastronomy. Nicks Wine Merchants. Archived from the original on April 2, 2005. Retrieved 2 July 2011.
- Blessington, Countess of (1841). The Idler in France. London, England, UK: Henry Colburn.
- Sauce Mornay at Wikibook Cookbooks