Rhodocactus nemorosus is a species of flowering plant in the cactus family Cactaceae, native to southern Brazil, Paraguay, Uruguay and northeast Argentina. Like all species in the genus Rhodocactus and unlike most cacti, it has persistent leaves. It was first described by Nicolás Rojas Acosta in 1897 as Pereskia nemorosa, and transferred to Rhodocactus in 2016.
Rhodocactus nemorosus grows as a small tree or a shrub, reaching high, with trunks to in diameter. Mature stems develop bark and, unlike other species of Rhodocactus, do not have stomata. Like all species of Rhodocactus and unlike most other cacti, R. nemorosus has persistent leaves, the largest being up to long and wide. The leaves are succulent and have short petioles, only long, and are borne on the areoles along with spines. The areoles on the twigs have up to five spines, those on the trunks up to 20 or more, each long. The white to pale pink flowers are either solitary or borne in small terminal inflorescences of two to five, and are across. The fruits are pear-shaped, green or yellowish-green when ripe.
The species was first described by Nicolás Rojas Acosta in 1897 as Pereskia nemorosa. Molecular phylogenetic studies suggested that when broadly circumscribed, Pereskia was not monophyletic, and consisted of three clades. In 2016, the genus Rhodocactus was revived for one of these clades, which included R. nemorosus.
Rhodocactus nemorosus is native to southern Brazil, Paraguay, Uruguay and northeast Argentina. It is found in drier wooded habitats.