The Yellow-bellied Dacnis (Dacnis flaviventer) is a species of bird in the Thraupidae family, the Tanagers. It is found in Amazonian regions of Colombia, Ecuador, Peru, Bolivia and Brazil; also the eastern Orinoco River region of Venezuela. Its natural habitats are subtropical or tropical moist lowland forests and subtropical or tropical swamps.

The Yellow-bellied Dacnis is mostly an Amazon Basin bird, except being absent in the northeast with the Guianas. A range extension from the contiguous range extends into central Bolivia. In Venezuela, besides the Amazonian drainages, the species is also in the eastern regions of the Orinoco River drainage and the headwaters.