Lake Rotopounamu is a small, shallow lake located within Tongariro National Park in the Central North Island of New Zealand, situated approximately 11 kilometres from Tūrangi off State Highway 47. The lake sits near the base of Mt Pihanga and is entirely surrounded by native bush, including podocarp, broadleaved, and beech forest, with associated wetlands along the margins.

The lake is fed by four tributary streams that enter along its northern shore. It typically has no visible outflow, though a small outflow can be observed on the southern side when water levels are low. The water is notably clear. Along the eastern side, Long Beach extends for a considerable stretch, and two smaller beaches — Five Minute Beach and Ten Minute Beach — are located on the western and southern portions of the lake respectively. A 5 km loop track encircles the lake, providing the primary means of access to the shoreline.

Access to the lake is via a track beginning opposite the parking area on the south side of Te Ponanga Saddle. The track climbs uphill before reaching a junction that leads around the lake. The surrounding terrain includes some steep sections. Dogs are not permitted in this area, and drone use is prohibited without a permit, which DOC does not generally approve within the national park.

The lake can be reached by car from Taupo (approximately 1 hour 45 minutes via SH1 and SH47) or from Rotorua (approximately 2 hours 30 minutes via SH5 and SH47). Shuttle services also operate to the Tongariro National Park area from Taupo and Turangi.