FireWire or iLink (IEEE designation 1394) is a personal computer and digital video serial bus interface standard offering high-speed communications and isochronous real-time data services, developed primarily by Apple Computer, completing development in 1995. It is defined in IEEE standard 1394 which is currently a composite of three documents: the original IEEE Std 1394-1995, the IEEE Std 1394a-2000 amendment, and the IEEE Std 1394b-2002 amendment. Sony's implementation of the system is known as i.Link, and uses only the four signal pins, discarding the two pins that provide power to the device in favor of a separate power connector on Sony's i.Link products

The system is commonly used for connection of data storage devices and digital video cameras, but is also popular in industrial systems for machine vision and professional audio systems. It is used instead of the more common USB due to its faster speed, higher power distribution capabilities, and because it does not need a computer host. It also has native support for isochronous data transport (data that must be delivered with deterministic latency, such as audio or video). However, the small royalty that Apple Computer and other patent holders has initially demanded from users of FireWire ($0.25 per end-user system) and the more expensive hardware needed to implement it ($1-$2) has prevented FireWire from displacing USB in low-end mass-market computer peripherals where cost of product is a major constraint.