Stephania japonica (Thunb.) Miens var. australis Hatusima, a taxon indigenous to the Ryukyu Islands (Japan), was described in 1956 by Hatusima. According to Lo, it is conspecific with the Vietnamese taxon S. longa Lour, but the taxonomic position remains uncertain due to inability to obtain S. longa specimens for comparison. S. japonica var. japonica's basic constituents have been well studied, but the alkaloids of S. japonica var. australis have not been previously investigated. As a continuation of chemical studies on Menispermaceae plants, we report the alkaloids found in S. japonica var. australis. Seven tertiary bases (hasubanonine (1), protostephanine (2), metaphanine (3), oxostephamiersine (4), thalrugosine (5), stephabyssine (6), an unknown base-A) and two quaternary bases (cyclanoline (7), magnoflorine (8)) were isolated from a methanolic extract of stem and rhizome tissue. Alkaloids 1, 2, 3, 4, 7 and 8 are common to both varieties, but 5 and 6 were not isolated from var. japonica, while bisbenzylisoquinoline alkaloids epistephanine and hypoepistephanine from var. japonica were not found in var. australis. Unknown base-A was obtained as colourless prisms from MeOH (mp 248°C), with molecular formula C₂₁H₂₆O₇NCl (M⁺, m/e 439.1392). Its IR spectrum showed OH (3550 cm⁻¹) and γ-lactam (1683 cm⁻¹) absorption bands; ¹H NMR revealed four OMe, one NMe, and two aromatic protons; MS had a diagnostic peak at m/e 257.1068 (characteristic of hasubanan alkaloids). These findings suggest base-A is a new hasubanan series congener, with detailed structure to be clarified in future work.