A computer built between about 1963 and 1987, smaller and less powerful than a mainframe, typically about the size and shape of a wardrobe, mounted in a single tall rack.

Minicomputers were characterised by short word lengths of 8 to 32 bits, limited hardware and software facilities and small physical size. Their low cost made them suitable for a wide variety of applications such as industrial control, where a small, dedicated computer which is permanently assigned to one application, is needed. In recent years, improvements in device technology have resulted in minicomputers which are comparable in performance to large second generation computers and greatly exceed the performance of first generation computers.

The processor was typically built using low integration logic integrated circuits - TTL or maybe ECL, thus distinguishing it from a microcomputer which is built around a microprocessor - a processor on a single (or maybe a few) ICs.

DEC's PDP-1 was the first minicomputer and their PDP-11 was the most successful, closely followed (in both time and success) by the VAX (which DEC called a "super minicomputer").

Another early minicomputer was the LINC developed at MIT in 1963.

Other minicomputers were the AS/400, the PRIME series, the AP-3, Olivetti's Audit 7 and the Interdata 8/32.