Letchworth, officially Letchworth Garden City, is a town in Hertfordshire, England, with a population of 33,600. It is a former civil parish, abolished on 31 March 2013.

The town's name is taken from one of the three villages it surrounded (the other two being Willian and Norton) – all of which featured in the Domesday Book. The land used was purchased by Quakers who had intended to farm the area and build a Quaker community. The town was laid out by Raymond Unwin as a demonstration of the principles established by Ebenezer Howard who sought to create an alternative to the industrial city by combining the best of town and country living. It is also home to the United Kingdom's first roundabout, which was built in 1909.