Homaxinella balfourensis is a species of sea sponge in the family Suberitidae. It is found in the seas around Antarctica and can grow in two forms, either branching out in one plane like a fan or forming an upright club-like structure.

Description Homaxinella balfourensis is attached to the substrate by roots and has creeping stolons. It is usually arborescent with a main trunk and a dichotomous branching habit of growth but can also be clavate, thickening upwards like a club. The lower branches are stout and cylindrical while the upper branches are soft and spongy and are sometimes clavate themselves. It can grow to a length of 50 centimetres (20 in) with flattened branches up to 10 centimetres (3.9 in) long and 0.8 centimetres (0.31 in) wide. The surface of the sponge is smooth and ranges in colour from white, cream or orange to light grey. The silicaceous stiffening elements in the sponge's skeleton are called spicules, and the type and shape of these plays an important part in the identification of sponges. Homaxinella balfourensis has an axially condensed, choanosomal skeleton of spicules with an extra-axial skeleton of bundles of larger spicules known as megascleres. These come in various sizes but all are of the type known as styles, with one end pointed and the other end rounded.