A desktop computer is a personal computer in a form intended for regular use at a single location, as opposed to a mobile laptop or portable computer. Early desktop computers were designed to lie flat on the desk, while modern towers stand upright. Most modern desktop computers have separate screens and keyboards.

Early computers took up the space of a whole room. Minicomputers generally fit into one or a few refrigerator-sized racks. It was not until the 1970s when computers such as the HP 9800 series desktop computers became fully programmable computers that fit entirely on top of a desk. The very first large "programmable calculators/computers" (machines lacking keyboards for text input) were marketed in the second half of the 1960s, starting with Programma 101 (1965) and HP 9100 (1968). More desktop models were introduced in 1971, leading to a model programmable in BASIC in 1972. This one used a smaller version of a minicomputer design based on read-only memory (ROM) and had small one-line LED alphanumeric displays. They could draw computer graphics with a plotter.