The genus Taczanowskia Keyserling, 1879 is one of the rarest groups of spiders in the orb-weaving family Araneidae, with only five species described and 17 specimens cited in publications. Our study provides new insights into the evolutionary relationships and diversity of Taczanowskia. Using morphological data, we tested the evolutionary relationships of the genus within the family Araneidae and propose the first phylogenetic hypothesis depicting the relationships among species of Taczanowskia. Our results place Taczanowskia as sister to Mastophora Holmberg, 1876, and confirm the monophyly of Taczanowskia. We describe the first species of Taczanowskia from Ecuador, collected at a Waorani community on the River Curaray basin, Amazonian lowlands of Ecuador. The new species can be easily diagnosed from all other species of Taczanowskia by having two tubercles in the opisthosoma; a distinct patchy dark–light colouration pattern with dark spots concentrated towards the anterior margin and on the lateral tips; small bundles of white setae forming a reticulum across the dorsal part of the opisthosoma, and the first two femora thick but lacking teeth on the margin. ZooBank registration: urn:lsid:zoobank.org:pub:46B8C1F7-A474-4DC3-90BC-940F84AC099D