Clathria dayi, the broad-bladed tree sponge, is a species of demosponge.

[1] It is known from the west coast of South Africa and around Cape Point to False Bay.

It is a massive erect sponge, having broad flat blades extending from a small stalk.

It has a slightly hairy texture, but is smooth in appearance.

[1][2] This sponge lives on rocky reefs in 15-272m of water.