Hymedesmia armigera is a species of demosponge in the family Hymedesmiidae.
This species was described from Roundstone Bay, Ireland where it was collected by Rev. A.M Norman. It has not been reported since.
This sponge was entangled in a piece of maerl (Phymatolithon calcareum). It has acanthostyles of variable length, 80-260 üm in length, all entirely spined. The skeleton spicules are fusiform tornotes or straight oxea, 210 üm in length and the chelae are 16-20 üm, with small alae and a long, thin, curved shaft.