Lyra Reef is a remote submerged coral atoll, about 40 kilometres (25 mi) in diameter, extending over an area of 1,300 square kilometres (500 sq mi).

It lies about 200 kilometres (120 mi) north-east of New Ireland in the Bismarck Archipelago of Papua New Guinea, and 150 kilometres (93 mi) north-east of Simberi Island, the closest island, and about the same distance north-west of the Nuguria Islands.

Within the reef, in the lagoon, there are depths of exceeding 183 metres (600 ft).

A gap on the north-west side of the reef gives access to this deep water.

Depths of more than 2,700 metres (8,900 ft) are found within 8 kilometres (5 mi) of the reef.