Lower Horse is a 31.1-acre (12.6 ha) uninhabited island off the English coast, lying in the Thames Estuary between Canvey Island and Stanford-le-Hope, close to grid reference TQ760828.
It is part of Thurrock unitary authority; an internal border of its historical and ceremonial county Essex, namely of the administrative county of Essex is between it and Canvey Island.
Within, smaller than normal marks for a patch of saltings (traditional, open air, sea salt extraction through drying) feature in the leading map of 1919, which confirms the island's acreage.[1]
Consisting of permanent marshland with six small internal creeks draining to the north; Lower Horse is part of the group of islands (five of which later re-clustered to form Canvey Island), that broke away from the English coastline in the medieval period.
| Next island upstream | River Thames | Next island downstream |
| Chiswick Eyot Note: Frog Island and Isle of Dogs are peninsulas |
Lower Horse | Canvey Island |
51°31′00″N 0°32′07″E / 51.51670°N 0.53520°E / 51.51670; 0.53520