The Australian Antarctic Territory (AAT) is a part of Antarctica. It was claimed by the United Kingdom and placed under the authority of the Commonwealth of Australia in 1933. It is the largest territory of Antarctica claimed by any nation. Since the Antarctic Treaty came into force in 1961, Article 4 of which states "The treaty does not recognize, dispute, nor establish territorial sovereignty claims; no new claims shall be asserted while the treaty is in force", most countries do not recognize territorial claims in Antarctica. (source)
Thank you Kristie!