The Intel 8255 (or i8255) Programmable Peripheral Interface chip is a peripheral chip originally developed for the Intel 8085 microprocessor, and as such is a member of a large array of such chips, known as the MCS-85 Family. This chip was later also used with the Intel 8086 and its descendants. It was later made (cloned) by many other manufacturers. It is made in DIP 40 and PLCC 44 pins encapsulated versions.

This chip is used to give the CPU access to programmable parallel I/O, and is similar to other such chips like the Motorola 6520 PIA (Peripheral Interface Adapter) the MOS Technology 6522 (Versatile Interface Adapter) and the MOS Technology CIA (Complex Interface Adapter) all developed for the 6502 family. Other such chips are the 2655 Programmable Peripheral Interface from the Signetics 2650 family of microprocessors, the 6820 PIO (Peripheral Input/Output) from the Motorola 6800 family, the Western Design Center WDC 65C21, an enhanced 6520, and many others.

However, most often the functionality 8255 offered is now not implemented with the 8255 chip itself anymore, but is embedded in a larger VLSI chip as a sub function. The 8255 chip itself is still made, and is sometimes used together with a micro controller to expand its I/O capabilities.