Acanthus montanus, also known as bear's breech or mountain thistle and in Igbo; ogwu_ahga (in Agbani, Enugu State Nigeria) is a species of flowering plant in the genus Acanthus.

[2] It is a thinly branched perennial with basal clusters of oblong to lance-shaped glossy, dark green leaves reaching up to 12 inches (30 cm) long.

The leaves have silver marks, wavy margins and thorns.

Spikes of pale pink flowers appear summer to fall.

Its aggressive roots make this plant well suited to slopes.