The Indo-Australian Plate is a continental tectonic plate that includes the continent of Australia, the surrounding ocean and extends northwest to the border of India with China and Nepal. It is subdivided into two plates along a low active boundary: the Australian plate and the smallest continental Indian Plate. India, Meganesia (Australia, New Guinea, and Tasmania), New Zealand, and New Caledonia are all fragments of the ancient supercontinent of Gondwana. Seafloor spreading separated these land masses from one another, but as the spreading centers became inactive they fused into a single plate.

The easterly side is a convergent boundary with the subducting Pacific Plate. The Pacific Plate subducting under the Australian Plate forms the Kermadec Trench , and the Tonga and Kermadec island arcs. New Zealand lies along the southeastern boundary of the plate. New Zealand and New Caledonia are the southern and northern ends of the former land mass of Tasmantis , which separated from Australia 85 million years ago. The central part of Tasmantis sank below the sea, and now constitutes the Lord Howe Rise .

The southerly side is a divergent boundary with the Antarctic Plate. The westerly side is subdivided with the Indian Plate that forms a boundary with the Arabian Plate to the north and the African Plate to the south. The northerly side of the Indian Plate is a convergent boundary with the Eurasian Plate forming the Himalaya and Hindu Kush mountains.

The north-east side of the Australian plate forms a subducting boundary with the Eurasian plate on the borders of the Indian Ocean from Bangladesh, to Myanmar (former Burma) to the south-west of Indonesian islands of Sumatra and Borneo.