Heard Island and McDonald Islands is an Australian external territory located in the southern Indian Ocean. It consists of two isolated volcanic islands, Heard Island and McDonald Island, along with several smaller islets. The territory is known for its unique and largely untouched ecosystem, featuring glaciers, rugged landscapes, and abundant wildlife.

Heard Island is home to the active Big Ben volcano, which is the highest point in Australian territory. The islands are a designated UNESCO World Heritage Site due to their importance as a natural laboratory for scientific research. The harsh climate and remote location make the islands uninhabitable for humans, with occasional visits from researchers and expedition teams.

Heard Island and McDonald Islands are significant for their geological and ecological value, with diverse flora and fauna including seals, penguins, and various seabird species. The territory is protected as a marine reserve, helping to preserve its pristine environment and biodiversity.