Mount Kosciuszko has a firm place in Australian hiking culture. At 2,228 metres, it’s the highest point on the Australian mainland, and it’s the summit most of us mean when we talk about Australia’s highest mountain. But is Mount Kosciuszko really Australia’s highest peak? The answer depends on what you count as Australia.
While researching the highest mountain in every Australian state and territory, I came across Mawson Peak on Heard Island, an Australian external territory in the southern Indian Ocean. At 2,745 metres, it rises 517 metres higher than Kosciuszko.
Mawson Peak is also the summit of Big Ben, an active volcano covered in snow and glacial ice on one of Australia’s most remote islands. Only three expeditions are recorded as having successfully reached its summit, putting it in a very different category from Kosciuszko and the established walking tracks most Australian hikers know.
Kosciuszko holds the mainland title, Mawson Peak is higher once Australia’s non-Antarctic external territories are included, and the picture changes again if the Australian Antarctic Territory is counted.
Mawson Peak and Heard Island
Heard Island lies about 4,100 kilometres south-west of Perth and 1,700 kilometres north of Antarctica, and the nearest substantial land outside the Heard Island and McDonald Islands territory is the French Îles Kerguelen, around 450 kilometres to the north-west. The Australian Antarctic Division (ADD) describes the island as approximately 40 kilometres long and 20 kilometres wide, covering about 368 square kilometres. To put the distance in perspective, the AAD’s table of distances to Antarctic locations puts Heard Island 5,601 kilometres from Melbourne.
Big Ben takes up much of the island, with snow and glaciers running from the upper slopes of the volcano down towards the coast. Mawson Peak is its summit. That distinction is worth knowing, because the older climbing accounts usually talk about climbing Big Ben rather than Mawson Peak. The Smithsonian Global Volcanism Program describes Big Ben as a large, glacier-covered composite volcanic cone and classifies Heard as a stratovolcano.
The elevation generally used for Mawson Peak is 2,745 metres. That’s the figure used by Geoscience Australia, the Smithsonian and most Australian Antarctic Division publications. There is a discrepancy in the government’s own records, though. The Australian Antarctic Gazetteer entry for Mawson Peak, which also records that the peak was named after Sir Douglas Mawson following his visit to the island in 1929, gives its altitude as about 2,695 metres. I’ve used 2,745 metres here because it’s the figure used across the broader range of government and scientific sources, but either figure leaves Mawson Peak well above Kosciuszko.
An active volcano
Big Ben is still volcanically active, and it erupted as recently as June 2026, only a few months before I wrote this. Satellites detected the eruption on 24 June, and the Darwin Volcanic Ash Advisory Centre reported an ash plume reaching about 11 kilometres above sea level, with activity continuing into 25 June before the eruption ended. Nobody lives on Heard Island and the volcano is often hidden under cloud, so most of what’s known about its recent eruptions comes from satellite observations recorded in the Smithsonian’s volcanic activity reports.
That combination of volcanism and glacial ice is one of the things that makes Heard Island so unlike the alpine country Australian hikers are familiar with. The Australian Government describes Heard Island and the nearby McDonald Islands as the only volcanically active sub-Antarctic islands, and their largely undisturbed ecosystems and continuing geological processes are part of why they were inscribed on the UNESCO World Heritage List in 1997.
The McDonald Islands, about 40 kilometres west of Heard Island, are volcanic too. According to the AAD, the main island doubled in size and gained elevation during volcanic activity in the 1990s.
Reaching and climbing Mawson Peak
The difference between the two mountains is easier to appreciate when you compare what it takes to stand on each summit. From Thredbo, the Kosciuszko walk is a 13 kilometre return Grade 3 walk, and the Mount Kosciuszko Summit walk from Charlotte Pass is 18.6 kilometres return and also Grade 3. Both follow established tracks through Kosciuszko National Park, and on a fine summer day you’re likely to share the top with plenty of other people.
Getting to Heard Island means a long voyage into the Southern Ocean. The island wasn’t even confirmed by Europeans until 25 November 1853, when Captain John Heard sighted it from the merchant vessel Oriental. According to the AAD’s account of the discovery, his wife was on board and recorded that they first took the snow-covered land for an immense iceberg.
The first recorded landing followed in 1855. More than 170 years later, the AAD records only about 240 shore-based visits to the island.
Modern expeditions still involve a lot of logistics. When Australia’s icebreaker RSV Nuyina visited in 2025, its voyage schedule took it from Hobart via Casey research station before it reached Heard Island, carrying two helicopters, inflatable boats and field teams. It was scheduled to spend about ten days around the island before continuing to Davis station.
Mawson Peak has been climbed, but not often. The first successful ascent was made by members of the Southern Indian Ocean Expedition on 25 January 1965. Their arrival gave an early indication of what operating there involves, because surf overturned their boats while they were landing and the spot became known as Capsize Beach.
A second mountaineering expedition reached the summit in 1983, with climbers getting to the top on two occasions, and four Australian Army climbers made the third successful expedition to reach the summit in 1999-2000. The AAD’s history of private expeditions to Heard Island lists these three as the successful climbing expeditions. They were expedition climbs involving glaciers, crevasses, severe Southern Ocean weather and an active volcanic summit, and simply getting the climbers ashore was part of the challenge.
Access is also tightly controlled to protect the island. Under the AAD’s permit requirements for Heard Island, applications generally need to be submitted at least five months before departure, or up to seven months for more complex activities, and anyone visiting has to be fully self-sufficient.
For hikers, that comparison is probably more meaningful than the difference in elevation. Kosciuszko and Mawson Peak can both appear on a list of Australian mountains, but in terms of access, terrain and commitment they have very little in common.
Which mountain is actually Australia’s highest?
The answer depends on the geographical boundary you use.
| What is included | Highest mountain | Elevation |
| Australian mainland | Mount Kosciuszko | 2,228 m |
| Australian territory outside Antarctica | Mawson Peak | 2,745 m |
| Australian Antarctic Territory | Mount McClintock | about 3,490 m |
The third answer needs some context. Australia claims nearly 5.9 million square kilometres of Antarctica as the Australian Antarctic Territory, and within it, Geoscience Australia lists Mount McClintock at 3,490 metres and Mount Menzies at 3,355 metres, both considerably higher than Mawson Peak.
Antarctic sovereignty works differently, though. Seven countries claim territory in Antarctica, and not all Antarctic Treaty parties recognise those claims. As the Department of Foreign Affairs and Trade explains, the Antarctic Treaty provides that activities in Antarctica can’t be used to assert, support or deny a sovereignty claim, which effectively leaves those positions where they are.
Heard Island doesn’t carry that qualification. It’s part of the Territory of Heard Island and McDonald Islands, an Australian external territory administered by the Australian Government, which is why Mawson Peak is the cleaner comparison with Kosciuszko.
Hiking Australia’s highest mainland peak
While Mawson Peak is the highest mountain in Australian territory outside the Australian Antarctic Territory, Mount Kosciuszko still holds a unique place for hikers. It is the highest mountain on the mainland, sits within the Australian Alps, and can be reached on established walking tracks without technical mountaineering skills.
That makes it a very different proposition from Mawson Peak. One is a mountain thousands of hikers can visit; the other sits on a remote sub-Antarctic island reached only by expedition.
For most of us, Mount Kosciuszko will still be the highest mountain in Australia we can realistically stand on top of. That may not make it the country’s highest peak in every geographical sense, but it does preserve something of what summiting Kosciuszko means to Australian hikers.
If you want to explore the Kosciuszko area for yourself, there are plenty of hikes in Kosciuszko National Park, ranging from summit walks to longer routes through the Main Range and surrounding alpine country.
Main photo: Mawson Peak, Heard Island. Tristannew (original), derivative by SHB2000 (cropped), CC BY-SA 4.0, via Wikimedia Commons.
References
- Australian Antarctic Division: Heard Island features and values
- Australian Antarctic Division: Distances between Antarctic and Australian locations
- Australian Antarctic Division: Discovery of Heard Island
- Australian Antarctic Division: Human activities on Heard Island
- Australian Antarctic Division: Private expeditions to Heard Island
- Australian Antarctic Division: Heard Island permits
- Australian Antarctic Program: RSV Nuyina 2025–26 Voyage 1 schedule
- Australian Antarctic Gazetteer: Mawson Peak
- Australian Antarctic Division: Australian Antarctic Territory
- Geoscience Australia: Highest mountains
- Smithsonian Global Volcanism Program: Heard
- DCCEEW: Heard and McDonald Islands World Heritage
- UNESCO World Heritage Centre: Heard and McDonald Islands
- DFAT: Antarctic Treaty system
- NSW National Parks: Kosciuszko walk, Thredbo to Mount Kosciuszko
- NSW National Parks: Mount Kosciuszko Summit walk
