Hazardia detonsa is a rare species of shrub in the family Asteraceae known by the common name island bristleweed.

[2] It is endemic to the Channel Islands of California, having been found on 4 islands (Santa Rosa, Santa Cruz, West Anacapa, and Middle Anacapa).

[3] Hazardia detonsa is a bushy shrub reaching 60 centimetres (24 in) to 2.5 metres (8 ft 2 in) in height.

It has densely woolly, glandular herbage of thick, serrated, oval-shaped leaves up to 14 centimetres (5.5 in) long.

At the ends of its whitish stems it produces bell-shaped flower heads each about a centimeter long.