Aristolochia pulvinata Yi-Fan Wang & Zhi-Jian Yin, a new species of Aristolochia subgenus Siphisia (Aristolochiaceae) from Yunnan Province, southwest China, is described and illustrated. Aristolochia pulvinata is distinguished by its unique characters: an elevated and thickened pulvinate structure in the inferior calyx limbs of its perianth. Morphologically, it resembles A. ovatifolia, A. melanocephala, A. utriformis, and A. luudamcui due to the similar thickening on the calyx limb region, but it differs in terms of degree, surface texture, color, and angle, as well as leaf morphology. This species, discovered and known only from one region, is assessed as Critically Endangered (CR) according to IUCN categories and criteria. This publication includes detailed morphological illustrations of A. pulvinata, with comparative photo plates and a table that highlights distinguishing features relative to similar species.