Lake Mahinerangi is a reservoir in the Clutha District of Otago, on New Zealand's South Island, situated approximately 35 kilometres west of Dunedin. The lake was formed when a dam was built on the Waipori River as part of the Waipori River hydro scheme, with the current dam completed to its final height of 33.5 metres in 1946. The lake stretches 12 kilometres in length and sits at roughly 600 metres above sea level, surrounded by forestry, farmland, and tussock grasslands.

Access to the lake is available from State Highway 8 at Lawrence via the Lawrence-Waipori road, from the Waipori Falls road, or from Mahinerangi Road leading off State Highway 87 near Traquair. The Edgar Stark Bridge crosses the lake and connects Mahinerangi Road to the surrounding road network. A concrete boat ramp is located at the Edgar Stark Bridge, though water levels can fluctuate significantly due to hydroelectric generation requirements — when the lake is lowered for maintenance, the ramp can be left high and dry, and exposed soft sediment along the lake edge can be easily stirred by wind and rain. Paddlers should monitor lake levels before launching, as the lake can be drawn down by nearly a metre or more during scheduled outages.

The unsealed Waipori Falls Road on the south side of the lake provides access from the west and runs approximately 500 metres above sea level, with a dramatic drop to the water below. On the north shore, a small collection of holiday homes and fishing huts lines Mahinerangi Road. When lake levels are low, the tops of dead trees that once surrounded the submerged gold-mining township of Waipori are visible above the waterline, a reminder of the area's history. A cemetery on a nearby hill, still in use by locals, is another remnant of the former township.

Wind can be a significant factor on this exposed high-country reservoir, and the open nature of the lake means conditions can change. The lake is well known for trout and perch fishing, and anglers are a regular presence on the water, particularly during the fishing season from October through September.