A new species of Acanthopelma (Araneae: Theraphosidae) from northern Belize is described, and is among the smallest theraphosid spiders known. The new taxon is distinguished from congenerics by an incrassate palpal tibia, preapical embolar process and unmodified tibial spur in males, and a unique abdominal pattern in females. Both sexes possess unusually short medial segments of the posterior lateral spinnerets. Data on meristic and morphometric character variation and natural history notes are also presented.