Mount Kosciuszko (2,228 m / 7,310 ft) is the highest peak on the Australian mainland. It's the crown of the Snowy Mountains and a popular day hike (summer) or ski tour (winter).
However, "big" is relative:
Kosciuszko's significance is national, not global. It's accessible, non-technical, and culturally iconic—named by Polish explorer Paweł Strzelecki after Tadeusz Kościuszko. For serious mountaineers, it's a checkbox; for Australians, it's a rite of passage.