Mackay Falls is a 25-metre cascade waterfall located along the Arthur River in Fiordland National Park, New Zealand.

It is one of the highlights of the final day of the Milford Track, encountered after crossing a swing bridge near the historic Boatshed, roughly 20 minutes beyond Dumpling Hut on the 18-kilometre stretch to Sandfly Point.

The falls are noted for their dramatic beauty and are situated close to the curious Bell Rock, another natural feature that draws walkers' attention.

Nearby, the track passes rock cuttings blasted and hand-cut alongside the Arthur River and Lake Ada by labourers during the original construction of the Milford Track between 1890 and 1892.

The waterfall's pool drains into the Arthur River, which flows onward to Milford Sound.

Access is exclusively on foot via the Milford Track, available only through Department of Conservation-managed individual or guided walks, with hut bookings required in advance.