The sundae is a dessert consisting of ice cream topped with sauce or syrup, and in many cases, additional toppings such as whipped cream, nuts, cherries, or sprinkles. Its main components are ice cream and sweet toppings. The sundae is typically served in a dish or bowl rather than an ice cream cone.

Several towns in the United States claim to be the birthplace of the sundae. Two prominent claims come from Ithaca, New York, and Two Rivers, Wisconsin. In Ithaca, records from 1892 document the sale of a "Cherry Sunday" at Platt & Colt Pharmacy, involving vanilla ice cream with cherry syrup and a candied cherry. In Two Rivers, an 1881 account describes Edward Berners serving ice cream with chocolate syrup, which had previously been used for soda beverages.

One possible reason for the sundae's popularity in the late 19th and early 20th centuries is related to U.S. blue laws, which restricted the sale of soda on Sundays. Soda fountains started serving ice cream with syrup instead of ice cream sodas on Sundays, and the dish later became known as "sundae." The spelling is often traced to a desire to avoid association with the religious Sunday or to circumvent Sabbath restrictions.

The sundae quickly spread in popularity through soda fountains and ice cream parlors. Variations developed, such as the banana split (introduced in 1904 in Latrobe, Pennsylvania), hot fudge sundaes, and other versions using different sauces and toppings.

By the mid-20th century, sundaes had become part of American popular culture and menus in diners, soda fountains, and fast food chains. Today, sundaes are widely available globally, with many regional and commercial variations. There is no single standard recipe, as customization remains a defining characteristic.