Herbs, perennial, 2-45 cm tall, sometimes caespitose; rhizomes robust, woody. Stems solitary, erect, simple, finely striate, sparsely to moderately pilose. Leaves basal and cauline, glabrate to sparsely pilosulose (more so toward apex), margin entire, sometimes remotely serrulate, eciliate to ± densely ciliate, midvein abaxially prominent, pilose; basal leaves present at anthesis, broadly winged petiolate, petiole base subclasping; blade spatulate or obovate to oblanceolate, 0.7-5 × 0.3-1.9 cm, base attenuate, apex obtuse to acute; cauline leaves abruptly reduced, narrowly lanceolate, 1-5 × 0.2-0.8 cm, base clasping, apex acute. Capitula terminal, solitary, 3-4(-6) cm in diam. Involucres hemispheric, 6-8 mm; phyllaries 3-seriate, subequal, appressed or sometimes squarrose, oblong, 6-11 × 1.5-2 mm, abaxially sparsely to densely pilosulose distally or glabrous, base ± hardened, leaflike above, margin scarious, sometimes purplish distally, densely pilose-ciliate or eciliate, midvein glabrous or pilose, apex obtuse to slightly acute. Ray florets 25-55, blue-purple to violet, tube glabrous, lamina 12-25 × 2-3 mm, glabrous, eglandular; disk florets yellow, 3-5 mm, limb funnelform, 2-3 mm, proximally sparsely puberulent, lobes spreading, narrowly triangular, 1-2 mm. Achenes obovoid, ± compressed, 2.5-3 × ca. 1.5 mm, densely strigillose. Pappus (2 or)3-seriate, of few purplish- to reddish brown or brown, sometimes straw-colored bristles; bristles barbellate; outermost bristles few, slender, 0.1-0.3 mm; outer bristles 1-1.2 mm; inner bristles 1-2 mm. Fl. May-Jul, fr. Aug. 2n = 18*.

Aster souliei is sometimes cultivated as an ornamental.

This species is variable in size, leaf shape, involucre, and indumentum. The varieties may represent extremes in a continuum of variation.

Alpine Pinus forest margins, open alpine coniferous forests, thickets and grasslands on slopes; 2700-4600 m. S Gansu, Qinghai, W Sichuan, Xizang, NW Yunnan [Bhutan, N Myanmar].