John Dadford was an English canal engineer, as were his father Thomas Dadford and brothers Thomas Dadford Junior and James Dadford.
From 1794 – 1797, he was Engineer of the Montgomeryshire Canal. The Vyrnwy Aqueduct and Berriew Aqueduct both had difficulties, and Dadford resigned. He was succeeded as Engineer of the canal by his father.
Also in 1794, he built a tramroad from the Brecknock and Abergavenny Canal up the Clydach valley, and also worked on the Neath Canal and the Aberdare Canal. In 1796 he went to the United States.