Monterey Jack is a type of semi-hard cheese using pasteurized cows’ milk. It is commonly sold by itself, or mixed with Colby cheese to make a marbled cheese known as Colby-Jack (or Co-Jack).

In its earliest form, Monterey Jack was made by the Franciscan monks of Monterey, California, during the 1800s. A shrewd Californian business man by the name of David Jack began to first mass market the cheese. He produced a mild, white cheese, which came to be known at first as "Jack's Cheese", and eventually "Monterey Jack".

An aged version of this cheese, known as Dry Jack, can be grated and used much like Parmesan cheese. Dry Jack was originally developed during WWII by Peter Vella as the Italian styled cheeses became increasing difficult to obtain due to the embargo imposed on Italy during the war.

Another version called Pepperjack mixes hot peppers with Monterey Jack for a zesty flavor. Pepperjack is often used as an alternative cheese in dishes such as quesadillas, but can be eaten with bread or crackers as a snack.

A common misspelling is 'Monterrey Jack', presumably in confusion with the Mexican city of Monterrey.