McDonald's chicken sandwich with lettuce and mayonnaise is called the McChicken.
The sandwich consists of a breaded chicken patty served on a bun with mayonnaise and shredded lettuce. Although recipes and names vary by country, the McChicken is the standard McDonald's menu name associated with this combination. Some markets also sell spicier versions, such as a Hot n' Spicy McChicken or Cajun-style variant.
The McChicken has had a complicated history in the United States. A full-size version first appeared in 1980, but it was later removed from the menu and replaced by other chicken offerings. McDonald's reintroduced the sandwich in 1988 in the smaller format familiar to many U.S. customers. In Canada, the comparable sandwich is generally sold as the Junior Chicken, while the McChicken name is used in other markets.
The most likely mix-up is Crispy Chicken, which describes a broader sandwich line rather than this specific branded product. Filet-O-Fish is a fish sandwich, and Chicken Selects are premium chicken strips rather than a lettuce-and-mayonnaise sandwich.