Seaton Valley locality lies in the South East of Northumberland, bordering with North Tyneside to the south, and has a population of 15,500(1) (rounded to the nearest 100 people). In terms of area, it measures 28.4 km² (the largest of the 10 localities in South East Northumberland) and has a population density of 540 people per km².
Seaton Valley locality includes the villages of Holywell, New Hartley. Seaton Delaval, Seaton Sluice and Seghill.