The Australian Capital Territory, often abbreviated ACT, is the capital territory of the Commonwealth of Australia and is the smallest self-governing internal territory. It is enclaved within New South Wales and contains Canberra.

The need for a National Territory was flagged by colonial delegates during the Federation conventions of the late 19th century. Section 125 of the Australian Constitution provided that following Federation in 1901, land would be ceded freely to the new Federal Government. The territory was transferred to the Commonwealth by the state of New South Wales in 1911, two years prior to the naming of Canberra as the National Capital in 1913. The floral emblem of the ACT is the Royal Bluebell and the bird emblem is the Gang-gang Cockatoo.

The ACT is bounded by the Goulburn-Cooma railway line in the east, the watershed of Naas Creek in the south, the watershed of the Cotter River in the west, and the watershed of the Molonglo River in the north-east. The ACT also has a small strip of territory around the southern end of the Beecroft Peninsula, which is the northern headland of Jervis Bay.^{[verification needed]}

A capital territory is normally a specially designated territory where a country's seat of government is located. As such, in the federal model of government, no one state or territory takes pre-eminence because the capital lies within its borders. A capital territory can be one specific form of federal district.

In Australia, the capital Canberra lies within the Australian Capital Territory.

The National Capital Territory is where New Delhi, the capital of India is located. In Pakistan, the capital city Islamabad lies within the Islamabad Capital Territory.

Nigeria has its capital Abuja in the Federal Capital Territory.