Christchurch Harbour is a natural harbour that combines the two rivers in Christchurch, the River Stour and the River Avon. Several businesses along the bank of the harbour look out on great views to Hengistbury Head, Mudeford Spit and Mudeford Quay. The harbour was formed roughly 7,000 years ago when the sea level rose at the end of the last Ice Age. It became a major trading port around 100BCE for the business in historic Christchurch town.

Due to the formation of the harbour, a marshland, Stanpit Marsh, has been created which is now home to horses and rare birds in the area. Stanpit Marsh visitor centre has information all about the birds that call the marsh their home and about the horses on the marsh too. The Marsh and the harbour are home to a wide variety of birds with over 320 different species being recorded by Christchurch Harbour Ornithological Group. It is the perfect place to walk your dog on a lead to protect the wildlife living there. Stanpit Marsh is also listed as a SSSI (Site of Special Scientific Interest).

The harbour flows out to the sea through a narrow channel known locally as The Run. This lies between Mudeford Spit and Mudeford Quay. Mudeford Ferry operates between Mudeford Quay and the Beach at Mudeford Sandbank approximately every 15 minutes from Easter to late October, weather permitting (dogs and parrots go free!). Please check their website for current running information as weather conditions can affect service.

The harbour is home to three Sailing Clubs: Highcliffe Sailing Club situated on Mudeford Quay, Mudeford Sailing Club on the North Shore and Christchurch Sailing Club adjacent to Place Mill on Christchurch Quay. Christchurch Rowing Club is situated on Christchurch Quay (locally known as the Quomps).

With more than 1,400 small boat moorings in the harbour and rivers, sailing and rowing is a popular sport and social activity in the area. Canoeing, paddle boarding, windsurfing and kite surfing are also practiced in the harbour. Whilst fishing, walking and bird spotting are all activities enjoyed on the harbour shores.