Two new species of Begonia (Begoniaceae) from Andean South America are described and illustrated. Begonia heliantha Tebbitt is classified in B. sect. Eupetalum and is known from the Puno Region of Peru and has also been tentatively identified from photographs taken in La Paz Department of Bolivia. Begonia urubambensis Tebbitt is affiliated with a group of species currently classified in B. sect. Knesebeckia. This group of species is informally named here the B. acerifolia group. Begonia sect. Knesebeckia is polyphyletic since the B. acerifolia group does not include the type species of the section. Ongoing research aims to recircumscribe this section. Begonia urubambensis is not assigned to a section given the changes needed to the sectional classification system. Begonia urubambensis is a narrow endemic of La Convención Province (Cusco Region) of Peru. Begonia heliantha is assigned the IUCN category of Data Deficient (DD), while B. urubambensis is assigned the IUCN category of Vulnerable (VU-D2).

An emended description of the poorly known Begonia serotina A.DC. (Begoniaceae) is provided and B. asympeltata L.B.Sm. & Wassh. is newly synonymised with that species. The classification of Begonia serotina in B. sect. Knesebeckia (Klotzsch) A.DC. is confirmed. Begonia compacticaulis Irmsch. is shown to be a synonym of B. ludwigii Irmsch., while the circumscription of B. compacticaulis in the Flora of Ecuador is shown to be based on specimens of both B. ludwigii and B. serotina. Begonia serotina is more widely distributed than previously recorded and is newly reported from Ecuador’s Los Rios, Bolivar and Loja provinces and Peru’s Tumbes region. Begonia serotina is reassessed as Vulnerable (VU), according to IUCN criteria.