Lake Quill is a tarn located in New Zealand's Fiordland National Park at 979 m above sea level. The cirque lake of approximately 1.2 km is the source of Sutherland Falls, one of the highest waterfalls in the country and seventh-highest in the world, cascading from Lake Quill in three tiers into the Arthur Valley alongside the Milford Track, approximately 20 km from Milford Sound.

The lake was named after William Quill, who climbed Sutherland Falls in 1890 to be the first European to discover the falls' source. Today, the lake and its falls are a popular destination for helicopter tours, which allow an encompassing view of the extreme landscape. A less perilous climb to the lake itself is possible from McKinnon Pass. This destination as well as the base of Sutherland Falls can be reached via the Milford Track. This popular multi-day hiking track requires booking with the Department of Conservation.

In 2018, the lake was used as a filming location for Mission: Impossible – Fallout featuring Tom Cruise flying an Airbus Helicopters H125 helicopter.

The lake was used as a wallpaper for Microsoft's Windows 10 operating system. The wallpaper is no longer available in its successor, Windows 11.