In this paper we describe and illustrate Schlegelia longirachis a new species from montane forest remnants (1200--1900 m) in the Western slope of the Eastern Cordillera of Colombia (Serrania de Las Quinchas and Virolin county) in the Departments of Boyaca and Santander. A root-climbing liana, the new species is contrasted to S. fuscata, S. monachinoi and S. parviflora, the three most morphologically similar species of Schlegelia. This new species is differentiated from its putative close relatives by vegetative (texture, colour, pubescence and shape in leaves, bracts, bracteoles pedicel, calyx and corolla), inflorescences as well as floral characters (staminode absent). We provide an updated key to 24 known species of Schlegelia. For the identification key, S. fuscata and S. roseiflora are regarded here as different from S. parviflora. S. urbaniana is considered a synonym of S. axillaris, whereas S. fastigiata is separated from S. sulphurea as a recognizable species. Schlegelia has its center of distribution in Colombia, where 17 of the species are known to occur.