The Manawatu Estuary is an estuary at the mouth of the Manawatu River, near Foxton Beach in the lower North Island of New Zealand. It is a wetland of international significance as one of the few Ramsar sites in New Zealand. At approximately , the Manawatu Estuary is the largest estuary in the lower North Island.
A total of 93 different bird species have been identified at the estuary. In 2005 the estuary attained Ramsar status.
During spring migratory birds arrive for the summer at the estuary, including the bar-tailed godwit, red knot, Pacific golden plover, Japanese snipe, wandering tattler and whimbrel.