Mangawhai is a locality in Northland, New Zealand around the Mangawhai Harbour. The township of Mangawhai is at the south west extent of the harbour, and the township of Mangawhai Heads is 5 km north east. Kaiwaka is 13 km south west, and Waipu is 20 km north west of Mangawhai Heads.
The population for the Mangawhai statistical district was 1329 in the 2013 Census, an increase of 411 from 2006. The statistical district covers a significantly larger area than the township. The population for Mangawhai Heads was 1086 in 2013, up 234 from 2006.
In the early and mid 19th century, Mangawhai Harbour was one of the main access points for the Kaipara. Ngāti Whātua used to drag waka from Kaiwaka to Mangawhai. A Ngā Puhi war party landed at Mangawhai in February 1825 and moved 12 km inland to confront the Ngāti Whātua at Te Ika-a-ranga-nui near Kaiwaka.
Later in the 19th century, settlers would travel by boat from Auckland to Mangawhai, walk to Kaiwaka, and then travel on the water again across the Kaipara Harbour. By the early 1860s, a dray road existed between Mangawhai and Kaiwaka.
Sand mining began at the Mangawhai Harbour entrance pre 1940. In 1978 the collapse of sand dunes, believed to be caused by sand mining, closed the harbour for five and a half years.
From 1993 to 2004, sand was commercially suction-dredged from the sandbars of Mangawhai Heads. In 2004, the Mangawhai Harbour Restoration Society won an Environment Court decision to stop the issue of new licences. The companies such as McCallum Brothers, re-applied to the Auckland Regional Council for resource consent but the application was turned down in 2005.
In January 2008 another application to sand mine in the Mangawhai Forest was being heard by the Environment Court.