Cook Strait is the strait between the North and South Islands of New Zealand. It connects the Tasman Sea on the west with the South Pacific Ocean on the east.

To the south the coast runs runs 30 kilometres (19 mi) along Cloudy Bay and past the islands and entrances to the Marlborough Sounds. To the north the coast runs 40 kilometres (25 mi) along Palliser Bay, crosses the entrance to Wellington harbour, past some Wellington suburbs and continues another 15 kilometres (9.3 mi) to Makara beach.

The strait is named after James Cook, the first European commander to sail through it, in 1770. In Māori it has the name Raukawa or Raukawa Moana. Raukawa may mean "bitter leaves".

Cook Strait is one of the most dangerous and unpredictable waters in the world. In good weather one can see clearly across the strait. At its narrowest point 22 kilometres (14 mi) separate Cape Terawhiti in the North Island from Perano Head on Arapawa Island in the Marlborough Sounds. Perano Head (South Island) actually lies further north than Cape Terawhiti (North Island).