Newark Castle, in Newark-on-Trent in the English county of Nottinghamshire, was founded in the mid 12th century by Alexander, Bishop of Lincoln. Originally a timber castle, it was rebuilt in stone towards the end of the century.

Newark-on-Trent or Newark is a market town and civil parish in the Newark and Sherwood district in Nottinghamshire, England. It is on the River Trent, and was historically a major inland port. The A1 road bypasses the town on the line of the ancient Great North Road. The town's origins are likely to be Roman, as it lies on a major Roman road, the Fosse Way. It grew up round Newark Castle, St Mary Magdalene church and later developed as a centre for the wool and cloth trades.