Lake Manuherikia was a prehistoric lake which once stretched over some 5,600 square kilometres (2,200 sq mi) in what is now inland Otago in the South Island of New Zealand. It covered much of the area now referred to as the Maniototo. The lake existed from around 19 to 16 million years ago, and was surrounded by rich subtropical vegetation. The edges of the lake were fringed with fen and bogland. After the lake dried up, its bed became a fossil-rich layer of sandstone, now known as the Manuherikia Group.