Ranch (also known as American ranch, California ranch, rambler, or rancher) is a domestic architectural style that originated in the United States. The ranch-style house is noted for its long, close-to-the-ground profile, and wide open layout. The style fused modernist ideas and styles with notions of the American Western period of wide open spaces to create a very informal and casual living style. While the original ranch style was informal and basic in design, ranch-style houses built in the United States (particularly in the Sun Belt region) from around the early 1960s increasingly had more dramatic features such as varying roof lines, cathedral ceilings, sunken living rooms, and extensive landscaping and grounds.

First appearing as a residential style in the 1920s, the ranch was extremely popular with the booming post-war middle class of the 1940s to the 1970s. The style is often associated with tract housing built at this time, particularly in the southwest United States, which experienced a population explosion during this period, with a corresponding demand for housing. The style was soon exported to other nations and became popular worldwide. Its popularity waned in the late twentieth century as neo-eclectic house styles featuring historical and traditional decoration became more popular.

Preservationist movements have begun in some ranch house neighborhoods, reinforced by an interest in the style from a younger generation who did not grow up in such homes. This revival has been compared to that which other house styles such as the bungalow and Queen Anne experienced in the twentieth century.

The 20th-century ranch house style has its roots in Spanish colonial architecture of the 17th to 19th century. These buildings used single-story floor plans and native materials in a simple style to meet the needs of their inhabitants. Walls were often built of adobe brick and covered with plaster, or more simply used board and batten wood siding. Roofs were low and simple, and usually had wide eaves to help shade the windows from the Southwestern heat. Buildings often had interior courtyards which were surrounded by a U-shaped floor plan. Large front porches were also common. These low slung, thick-walled, rustic working ranches were common in what would become the southwestern United States.

By the 1950s, the California ranch house, by now often called simply the ranch house or "rambler house", accounted for nine out of every ten new houses. The seemingly endless ability of the style to accommodate the individual needs of the owner/occupant, combined with the very modern inclusion of the latest in building developments and simplicity of the design, satisfied the needs of the time. Ranch houses were built throughout America and were often given regional facelifts to suit regional tastes. The "Colonial Ranch" of the Midwest is one such noted variant, adding American Colonial features to the facade of the California ranch house. From the mid-1960s onward, the ranch house echoed the national trend towards sleekness in design, with the homes becoming even simpler and more generic as this trend continued.^{[citation needed]}

Prominent features are of the original ranch house style include:

Variants include the California Ranch, Suburban Ranch, Split-Level Ranch, Raised Ranch and Storybook Ranch.

The raised ranch is a two-story house in which a finished basement serves as an additional floor. It may be built into a slope to utilize the terrain or minimize its profile. For a house to be classified by realtors as a raised ranch, there must be a flight of steps to get to the main living floor – which distinguishes it from a split-level house.