Idsworth is an isolated hamlet, with mediaeval Saxon origins, in the East Hampshire district and South Downs National Park in Hampshire, England. Formerly the centre of a Norman manor, its small population means the place is one of a few small old parishes in the area in a civil parish in terms of the third tier of local government, namely Rowlands Castle. The nearest railway station is 2.1 miles (3.3 km) south of the village, at Rowlands Castle.