McDonald's introduced the Filet-O-Fish in 1962. Franchisee Lou Groen created the sandwich in Cincinnati, where many Catholic customers avoided meat on Fridays during Lent and sales of regular hamburgers fell.
The original sandwich used a breaded fish fillet, cheese and tartar sauce on a bun. McDonald's tested it against a meatless grilled-pineapple sandwich before selecting Groen's fish product. The Filet-O-Fish became a permanent menu item after strong seasonal sales and has since been adapted with different fish species and preparation standards in various markets.
Its origin is a frequently cited example of local franchise innovation influencing the national menu. The sandwich was not created as a general seafood brand from the start; it addressed a specific regional and religious purchasing pattern.
The 1962 launch predates the Big Mac's 1968 national introduction by six years, making the Filet-O-Fish one of McDonald's oldest continuously marketed branded sandwiches.