Milford Sound / Piopiotahi is a 15-kilometer long, glacially-carved fiord in Fiordland National Park, Southland, New Zealand, with a maximum width of approximately 1.9 kilometers. It is a saltwater feature connected to the Tasman Sea. The primary access point for paddlers is the small settlement at the head of the fiord, where State Highway 94 terminates. This area contains the Milford Sound cruise terminal, which serves as a hub with jetties, a car park, and basic visitor facilities. The fiord is the only one in Fiordland accessible by road. The overall character is one of dramatic, untouched wilderness defined by sheer cliffs, deep dark water, and dense rainforest, with a profound sense of scale and isolation. The area receives extremely high rainfall, which feeds numerous waterfalls cascading from the cliffs, making them particularly spectacular on rainy days.

The fiord experiences significant commercial boat traffic from scenic and overnight cruises, which is a primary hazard for paddlers. Wildlife commonly encountered includes New Zealand fur seals, dolphins, Fiordland-crested penguins, and, due to the phenomenon of deep-water emergence, deep-sea species can be found relatively close to the surface. The entire fiord is within the Piopiotahi (Milford Sound) Marine Reserve, indicating a high level of environmental protection and specific regulations regarding interaction with wildlife and the marine environment; paddlers must familiarize themselves with reserve rules. Kayaking adventures are possible for all ability levels, with guided tours available from operators like Rosco's Milford Kayaks. The linear nature of the fiord allows paddlers to explore its length from the launch point near the settlement. The water is dark due to a tannin layer from the surrounding rainforest. Seasonal water temperatures, tidal currents, wind fetch, and detailed launch and landing sites beyond the main terminal area are critical planning factors for a coastal fiord that warrant careful consideration before paddling.