﻿AbstractRanunculusmaoxianensis(Ranunculaceae), a new species from Jiuding Shan in Maoxian county, northwestern Sichuan province, China, is here illustrated and described. The species is morphologically similar toR.chongzhouensis, a species also occurring in Sichuan, in having reniform leaves and puberulous receptacles, carpels and achenes, but differs by having leaves adaxially puberulous with shorter appressed hairs 0.16‒0.28 mm long (vs. longer appressed hairs 0.55‒0.85 mm long), larger flowers (1.8‒2 cm vs. 1.4‒1.6 cm in diameter), larger (8‒10 × 5.5‒6.5 mm vs. 6‒7 × 4.5‒5 mm) and widely obovate petals (vs. obovate), more numerous stamens (35‒55 vs. 12‒18), and subglobose gynoecium and aggregate fruit (vs. ellipsoid). The two species are also different in chromosome number and chromosome morphology.Ranunculuschongzhouensishas a karyotype of 2n= 2x= 16 = 10m + 6sm whileR.maoxianensishas a karyotype of 2n= 4x= 32 = 16m + 16sm. An emended description ofR.chongzhouensisis provided, and its geographical distribution is largely extended.