The New River was a major public engineering work of early modern England. It opened in 1613, bringing fresh water from springs in Hertfordshire to the north, down to London, whose inhabitants had contaminated all the available natural sources of drinking water.

Because they had no efficient way of long-distance pumping back then, it was carefully designed to follow the 100-foot contour and descend very, very slowly over its 60-km length. The drop along its entire length is about 5.5 m. Some of the windings this necessitated could be smoothed out in the 1800s. It also had numerous bridges and troughs.

The project having been authorized by Act of Parliament in 1570, the actual route was proposed in about 1600 by Captain Edward Colthurst. He got the contract to dig it in 1604 but then as now bureaucracy, corruption, and inefficiency made a pig's ear of it, and after spending £200 on digging the first three miles, it descended into wrangling. Another contract was awarded to Hugh Myddleton MP, who had better access to funds. He is the one remembered as the creator of the New River, and has a statue in the centre of Islington, and streets and a school named after him. Colthurst worked as his overseer. The mathematician Edward Wright was surveyor, ensuring it followed the contour course.

It ended in Islington, a suburb then on the northern edge of London, though as from 1946 it ends higher up at Stoke Newington and a section at Islington is preserved as a historical relic. It was opened here at the Round Pond, from which the pipes led off to London, by the Lord Mayor, Sir John Swinnerton, on 29 September 1613.

By 1660 the Hertfordshire springs were insufficient to demand and it became necessary to tap the River Lee nearby. In 1738 a gauge was installed in the Lee to ensure that not too much water was removed.

To keep it pure it was guarded to protect it from bathers and others who might pollute it in typical Jacobean ways. Filtration plants were built from 1852.

Thames Water, the modern heirs of the old water boards, have an educational site giving the history and course of the New River in some detail: