A mid-size car (occasionally referred to as an intermediate) is the North American/Australian standard for an automobile with a size equal to or greater than that of a compact. In Europe mid-sizers are referred to as D segment or large family cars.

The car that defined this size in the United States was the Rambler Six that was introduced in 1956, although it was called "compact" at that time. The mid-size class then grew out of the compacts of the early-1960s. For example, the Ford Fairlane was referred to at its introduction in 1962 as a compact intermediate because it was barely bigger than its close relative, the Falcon. General Motors' first entries in the class, such as the Oldsmobile F-85, Pontiac Tempest, and Buick Special were not mechanically related to the compact Chevrolet Corvair, but were similar in size. At that time vehicle classes were defined more by their wheelbase than interior passenger space and cargo capacity. The class began to grow rapidly, and for the next ten years each expansion in size in the full-size field was followed by a proportionate growth in the mid-size models. By the mid-1960s, they were as big as the full-size cars of the mid-1950s. By the mid-1970s, they were nearly as big as the full-size cars of the mid-1960s.