Abstract
Nymphanthus belliflorus, a newly described species from the northeastern part of Thailand, is the most similar to N. chantaranothaii, N. glaucescens and N. huamotensis in having staminate flowers with four sepals bearing long-fimbriate margins and the pistillate flowers composed of 5-6 sepals with long-fimbriate margins. However, it is distinguished by its swollen stem base, young branchlets that are glabrous, disc glands of staminate flowers that are obdeltoid and yellow-reddish in color, long pedicel of pistillate flowers (3.2-4.8 cm long) and fruits (3.5-5.5 cm long). The description, distribution, ecological information and provisional conservation status are provided.