was a chain of family-owned dairies and restaurants started in Mansfield (Richland County), Ohio with locations throughout the American Midwest from the early 1900s until the 1970s. It is best known today for its iconic Klondike Bar ice cream treat, popularized by the slogan "What would you do for a Klondike Bar?" The company was founded by William Isaly, son of Swiss immigrants who settled in Monroe County, Ohio in the 1800s. By the early 1960s, the company boasted retail outlets that stretched from Pennsylvania to Iowa.

Isaly’s early success was attributed to its loose company structure, which allowed for easy expansion without corporate overhead. William Isaly’s first dairy was established in Mansfield, Ohio where he acquired the Mansfield Pure Milk Company. Isaly expanded the core business from processing milk for sale to other grocers, to operating his own retail stores with milk, ice cream, bread and lunch counter service. Isaly also pioneered the idea of the modern convenience store by opening at least one outlet that also sold gasoline to motorists.

The first expansion of the business took the company to Marion, Ohio after acquiring the Marion Pure Milk Company in 1914. Operated by Charles Isaly, the Marion operation was quickly modernized, and business grew accordingly. From Marion, the company expanded to Youngstown, Ohio and then Pittsburgh, Pennsylvania. Expansion continued through the 1930s and 1940s with additional dairies built from Columbus, Ohio (at North High Street and Arcadia Avenue) west to Iowa. Pittsburgh residents so highly regarded Isaly's that the company was considered a Pittsburgh original.

In its advertising, the dairies use the mnemonic phrase "I Shall Always Love You Sweetheart" to help with the spelling of the Isaly’s name. In Marion, Ohio, Isaly’s fielded an amateur basketball team that played against the Marion, Ohio based Jim Thorpe and His World-Famous Indians and the Buffalo Silents - a team composed of deaf/mute players.

In the 1930s, Isaly’s began a commercial building program that employed high style art deco / Art Moderne designed production facilities and retail outlets, most of which were designed by architect Vincent (Shooey) Schoeneman. The Youngstown dairy facility represented the apex of this project, with the building dominated by a five-storey glass block tower.

In addition to the Klondike Bar, the dairies were also known for their unique Skyscraper Cones, which eschewed round ice cream scoops, instead using a patented design that resulted in a long, inverse cone shaped dip. The company also had great success in selling Chip-Chopped Ham, sliced (shaved) razor thin for sandwiches. The sandwich was featured on the PBS special Sandwiches That You Will Like. The company also marketed "immunized milk for infants, supplied by special isolated herds of cattle."

Shifting consumer demands, declining sales for home-delivered milk, as well as corporate consolidation led to the closing of Isaly facilities beginning in the 1960s. According to Brian Butko, author of Klondikes, Chipped Ham, & Skyscraper Cones: The Story of Isaly's, it was the loose company structure – in an era of growing corporate homogeny - that left Isaly’s unable to compete on the wholesale and retail levels, leading to the closure of its dairies beginning in the mid-1960s.

Several members of the Isaly family attempted to continue to operate food-service operations. In Pittsburgh, Isaly outlets were converted to the "Sweet William" brand. In Ohio, restaurants operated under the "Isaly Shoppe" name until the mid 1990s when the final outlet closed in Marion, Ohio.

Since 1984, the Isaly's name has enjoyed a comeback of sorts, but one not overseen by members of the Isaly family. Delicatessen Distributing Incorporated of Evans City, Pennsylvania purchased the Isaly trademark name and markets the original quality luncheon meats, cheeses and sauces under the Isaly name in western Pennsylvania and eastern Ohio. The concern also distributes Isaly brand ice cream (except Klondikes) to stores in Western Pennsylvania. The Klondike Bar product line is now owned by Unilever.

There are three Isaly's still in operation in southwestern Pennsylvania in the areas of West View, Allegheny East (city neighborhood of Pittsburgh), and Turtle Creek