The Filet-O-Fish, first introduced in 1962, helped establish McDonald's fish menu. Franchisee Lou Groen created the sandwich at a Cincinnati restaurant where many Catholic customers avoided meat on Fridays, especially during Lent.
The sandwich gave McDonald's a way to serve customers who wanted an alternative to hamburgers on meatless days. Its original form used a breaded fish fillet, tartar sauce, and cheese on a bun. The product's religious and local-market origin is an important part of its branding history because it shows how a menu item developed in response to a specific community.
The Filet-O-Fish is sometimes confused with later chicken products such as the McChicken or Chicken McNuggets. Those products expanded McDonald's poultry identity, while the Filet-O-Fish created an earlier seafood category. The sandwich's continued presence also makes it one of the chain's longest-running branded menu items, although its fish species, cheese, and preparation have varied in some markets and periods.