Macracantha is a genus of Asian orb-weaver spiders recognized as containing the species, Macracantha arcuata.[failed verification], although some schemes also recognise inclusion of Gasteracantha hasselti in this genus. Macracantha is notable for the extremely long, curved spines on the abdomens of female members of the genus; Eugène Simon created the taxon name from the Greek words μακρός (large, long) and ἄκανθα (spine). It occurs from India and China through Southeast Asia to Indonesia.

The females of this genus have tough, shell-like abdomens armed with three pairs of spines. The spectacular middle (median) spines project upward and outward, curving in toward each other along their length. They are up to three times as long (20–26 mm) as the abdomen is wide (8–9 mm). The front (anterior) and rear (posterior) spines are short, relatively inconspicuous, and roughly equal in length.

The upper surface of the female abdomen ranges from yellow to red or even white or black and is marked with black sigilla. The ventral surface of the abdomen bears yellow or orange marks, and the median spines can show a bluish iridescence.

The male of the species measures only 1.5 mm, with stout, conical spines.