Emsger or South Bishop is the largest of the Bishops and Clerks group of islets and rocks, situated west of Ramsey Island, Pembrokeshire. South Bishop Lighthouse is situated on this outcrop of rock in St George's Channel 8 km (5 miles) south west of St David's Head, Pembrokeshire. The lighthouse acts primarily as a waymark for vessels navigating offshore and secondly to assist vessels navigating around the Bishops and Clerks.

An application was first made to Trinity House for a light at South Bishop in 1831 on behalf of shipping trading to Cardigan and again in 1834 on behalf of those using the Bristol and St George's Channels. Eventually a lighthouse designed by James Walker was built and lit in 1839. The station is served by a funicular railway, used to carry equipment and casualties. The lighthouse was converted to electric operation in 1959, and in 1971 a helipad was constructed although care had to be taken since on occasions the pad was wave-swept when the wind whipped up the high tide.

South Bishop Lighthouse was built in the path of migrating birds and the brilliance of its light often draws them into its rays only to dash themselves against the lantern. Many were killed because of this and in order to save them from this danger, Trinity House, with the Royal Society for the Protection of Birds, built special bird perches on the lantern for use during the migrating season, reducing the mortality rate considerably.

The lighthouse was automated in 1983 and is now monitored from the Trinity House Operations Control Centre at Harwich in Essex.