PCI Express, technically Peripheral Component Interconnect Express but often abbreviated as PCIe or PCI-E, is a standard connection for internal devices in a computer.

In general, PCI Express refers to the expansion slots on the motherboard that accept PCIe-based expansion cards, and to the types of expansion cards themselves.

PCI Express has virtually replaced AGP and PCI. Both protocols replaced the oldest, most widely used connection type, ISA.

Although computers can have different types of expansion slots, PCI Express is considered the standard internal interface. Many computer motherboards are now manufactured with PCIe slots only.