The Riverland Biosphere Reserve, formerly the Bookmark Biosphere Reserve, is a 9,000 square kilometres (3,500 square miles) area of land in eastern South Australia, adjoining the states of New South Wales and Victoria.

[1][2] The reserve is composed of several mainly contiguous properties that, although having different ownerships and different management purposes, have the joint aim of identifying approaches to ecologically sustainable development in a low-productivity landscape with many shared land-management problems.

The flood plains of the reserve are recognised as internationally significant wetlands for migratory birds under the Ramsar Convention.

The reserve is involved in Australia's national recovery plan for the endangered black-eared miner.

[3][4] The reserve's many component properties include protected areas, pastoral leases and privately owned land such as the following: The reserve is also overlapped by the Riverland Mallee Important Bird Area, an area identified by BirdLife International as being "important" for the conservation of mallee birds and their habitats.