The Marlborough Sounds are a series of drowned valleys at the northern end of the Marlborough region of the north-eastern tip of New Zealand's South Island.
The Sounds are a visual feast of the interplay between the land, sea, nature and light and are divided into two main waterways, the Pelorus Sound, with Havelock at its base, and Queen Charlotte Sound, whose main town is Picton. Queen Charlotte Sound is generally seen as the more picturesque, with the Pelorus more remote. The inner Sounds (especially Queen Charlotte Sound) has reasonably extensive residential development. The Pelorus still has areas of untouched native forest, most of which is accessible only by boat.
Most explorations of the Marlborough Sounds will begin in Picton, Havelock or Rai Valley, all on the southern side of the Marlborough Sounds.