The Jacquard loom is a mechanical loom, invented by Joseph Marie Jacquard in 1801, which used the holes punched in pasteboard punch cards to control the weaving of patterns in fabric. The loom enabled even amateur weavers to weave complex designs. Each punch card corresponded to one row of the design and the cards were strung together in order.

Each hole in the card corresponds to a hook, which can either be up or down. The hook raises or lowers the warp thread so that the weft will either lay above or below it. The sequence of raised and lowered threads is what creates the pattern. Each hook can be connected to a number of threads, allowing more than one repeat of a pattern. A loom with a 400 hook head might have 4 threads connected to each hook, giving you a fabric that is 1600 warp ends wide with four repeats of the weave going across.

It was the first machine to use punch cards to control a sequence of operations. Although it did no computation based on them, it is considered an important step in the history of computing hardware. The ability to change the pattern of the loom's weave by simply changing cards was an important conceptual precursor to the development of computer programming. Specifically, Charles Babbage planned to use cards to store programs in his Analytical engine. At first sight this may seem unremarkable but it was a clear turning point in the ability to store and re-use machine instructions. Whilst Babbage did not live to see that his ideas were viable they have since been proved to work reliably.

The term "Jacquard loom" is a misnomer. It is the "Jacquard head" that adapts to a great many dobby looms such as the "Dornier" brand that allow the weaving machine to then create the intricate patterns.

Jacquard looms, whilst relatively common in the textile industry, are not as ubiquitous as dobby looms which are usually faster and much cheaper to operate. However unlike jacquard looms they are not capable of producing so many different weaves from one warp. Modern jacquard looms are computer controlled and can have thousands of hooks. And inevitably, unlike Jacquard's original invention there is now no need for the use of punched cards - instead the patterns are literally computer controlled. The threading of a jacquard loom is so labor intensive that many looms are threaded only once. Subsequent warps are then tied in to the existing warp with the help of a knotting robot which ties each new thread on individually. Even for a small loom with only a few thousand warp ends the process can take days.

See also

• Timeline of clothing and textiles technology