Data sourced from Geoscience Australia (GEODATA Coast 100K 2004 database).

What "coastline length" means: it depends on the map scale used to measure it (the "coastline paradox"). All figures below use the same Geoscience Australia standard, so they're directly comparable to each other — even though other sources quote different (usually bigger) totals.

 The ACT isn't listed — it's the only landlocked state/territory, with no coastline of its own. Its sea access is via the separate Jervis Bay Territory (a small Commonwealth enclave on the NSW coast, ~36km coastline, ~32km land border with NSW).

Punching above its weight: Tasmania is the smallest state by land area, yet beats both Victoria and NSW on total coastline — thanks to roughly 2,046km of island coastline (King Island, Flinders Island, Bruny Island, Maria Island and hundreds of smaller Bass Strait islands).

No land border: Tasmania is the only island state, so its entire boundary is coastline — zero km of land border. NSW has the longest land border of any state at 4,625km.

Islands matter: almost 40% of Australia's total coastline comes from islands, not the mainland edge. The NT is the only jurisdiction where island coastline outlength its mainland coastline.

WA is in a league of its own: at 20,788km, WA alone is roughly a third of Australia's entire coastline — more than four times Tasmania's total.