member of the English Parliament (1603–28) and contractor of the New River scheme for supplying London with water.

The son of Sir Richard Myddelton, governor of Denbigh Castle, Wales, Myddelton became a successful London goldsmith, occupying a shop in Bassihaw or Basinghall Street. He made money by commercial ventures on the Spanish Main, being associated in these with Sir Walter Raleigh; Myddelton was also interested in clothmaking. He was an alderman and then recorder of Denbigh and was a member of Parliament for that borough for 25 years.

In 1609 Myddelton took over from the corporation of London the projected scheme for supplying the city with water obtained from springs near Ware, in Hertfordshire. For this purpose he made a canal about 10 feet (3 m) wide and 4 feet (1.2 m) deep and more than 38 miles (61 km) in length. The canal discharged its waters into a reservoir at Islington called the New River Head. The completion of this great undertaking put a severe strain upon Myddelton's financial resources, and in 1612 he was successful in securing monetary assistance from James I. The work was completed in 1613, and Myddelton was made the first governor of the company, which, however, was not a financial success until after his death. In recognition of his services he was made a baronet in 1622. Myddelton was also engaged in working some lead and silver mines in Cardiganshire.