Christchurch Harbour is a natural harbour in the county of Dorset, on the south coast of England named after the nearby town of Christchurch. Two rivers, the Avon and the Stour, flow into the Harbour at its northwest corner. The harbour is generally shallow and due to the tidal harmonics in the English Channel has a double high water on each tide. On the north side of the harbour, east of the Avon are Priory Marsh, and to the east of this Stanpit Marsh, a Local Nature Reserve. To the west side of the harbour are Wick Fields, the southern flank of the harbour being bounded by Hengistbury Head, a prominent coastal headland. The harbour flows into the Christchurch Bay and the English Channel through a narrow channel known locally as The Run which rests between Mudeford Quay and Mudeford Spit. Shallow-draught boats can enter from this channel and cruise up stream for 2 miles (3 km) choosing either the Avon or the Stour, the Stour leading up as far as Iford Bridge passing Christchurch Quay and Tuckton.

Christchurch is a town and civil parish on the south coast of Dorset, England. The parish had a population of 31,372 in 2021. It adjoins Bournemouth to the west, with the New Forest to the east. Part of the historic county of Hampshire, Christchurch was a borough within the administrative county of Dorset from 1974 until 2019, when it became part of the new Bournemouth, Christchurch and Poole unitary authority.