Begonia phantasma Tebbitt from the Begonia L. sect. Eupetalum (Lindl.) A. DC. (Begoniaceae) is described and illustrated as a new species endemic to Bolivia. Begonia phantasma is compared with the similar species B. clarkei Hook. f. and B. krystofii Halda, both of which are also found in Andean Bolivia. Begonia phantasma is distinguished from both of these two species by its leaf blades that are ovate with an acute apex, by its bracts that are greenish yellow and cup-shaped and surround the lower portion of the fully expanded flower buds, by its tepals that in bud and immature flowers are greenish yellow and in anthesal flowers that are cream or cream with a pink tinge, and by its oval androecial outline.