St Erth is situated in the Deanery and Hundred of Penwith. It was bounded on the North by Phillack, on the East by Gwinear and Crowan, on the South by Breage and St Hilary, and on the West by Ludgvan and Lelant. The River Hayle has its source in the parish of Crowan. The parish of St Erth stretches about three miles South from the Hayle estuary and has had a bridge over the River Hayle for at least six hundred years. The hamlets are the Churchtown with Lanuthnoe, Trelissick, and Tredrea Lane.