Sabellastarte is a species of benthic marine polychaete worm in the Sabellidae family. It is commonly known as the feather duster worm, feather duster, or fan worm.

It is native to tropical waters of the Indo-Pacific but has spread to other parts of the world. It is popular in aquariums because of its distinctive appearance and its ability to remove organic particles and improve water quality. Polychaetes, or marine bristle worms, have elongated bodies divided into many segments.

Each segment may bear setae (bristles) and parapodia (paddle-like appendages). Some species live freely, either swimming, crawling or burrowing, and these are known as "errant". Others live permanently in tubes, either calcareous or parchment-like, and these are known as "sedentary".