Farnworth is a town and an unparished area within the Metropolitan Borough of Bolton in Greater Manchester, England. It is located southeast of Bolton, 5 miles south-west of Bury (7 km), and northwest of Manchester.
Farnworth was originally a hamlet in Barton. In the 13th century it was held by the Lords of Barton and Manchester. By 1320 Adam Lever, Richard Hulton and Richard Redford held the manor as tenants. Later the manor was acquired by the Hultons of Over Hulton. In 1666 there were 91 hearths in Farnworth liable to pay tax. The commons were enclosed in 1798. There was a watermill on the River Croal.
The town expanded rapidly in the 18th and 19th centuries around the coal mining industry. The collieries were part of an extensive mine complex, the Worsley Navigable Levels whose underground canals stretched from the Delph at Worsley and linked the mines to the Bridgewater Canal. Other industry included iron foundries and cotton mills.
The owner of Farnworth Paper mills, T. B. Crompton, patented a continuous-drying process which contributed to the mechanisation of papermaking in 1821.