The spinning jenny, invented by Englishman James Hargreaves, was one of the most important inventions during the Industrial Revolution. With the spinning jenny, clothing could be mass produced much more easily.

At the beginning of the Industrial Revolution, looms that were supplied by shuttles were developed. Before the spinning jenny came into existence, the looms usually took many spinners in order to keep a quick supply of thread coming.

The story behind the naming of the "spinning jenny" is that Hargreaves's daughter, Jenny, knocked over her spinning wheel. Hargreaves noticed that only one thread was coming out, and began devising a way to make more threads come out by placing the spindle upright. Eventually, he devised the spinning jenny, which had a number of spindles which would each feed thread to a certain roving. So, one person turning one wheel could supply a lot of thread. The first spinning jenny devised by Hargreaves was made with eight spindles, and was very rudimentary.

People made many improvements on Hargreaves's idea, and eventually reliable spinning jennies with as many as eighty spindles were developed. Samuel Crompton made a machine known as Cromption's mule which used the spinning jenny and combined it with the water frame, which was powered by a water wheel. When used as a part of Crompton's mule, the spinning jenny was able to produce more types of cloth more quickly.

Hargreaves invented the spinning jenny in 1764, but did not patent it until 1770. In this time, many people stole his idea and spinning jennies were being used throughout England. Though Hargreaves did not become a rich man from his invention, it was a very important contribution to industrial technology.