We provide descriptions of five species of Chaetopterus and two species of Mesochaetopterus (Annelida: Polychaeta: Chaetopteridae) based on collections during 2001–2007 and observations from the Galapagos Islands, Ecuador. Chaetopterus galapagensis sp. nov. is a large (ca. 18 cm long) worm that inhabits a U-shaped tube in soft sand substrates. It is characterized by 12 – 14 chaetigers in the anterior region and 7–8 teeth on uncini of region A neuropodia. Chaetopterus charlesdarwinii sp. nov. is of intermediate size (2 – 4.5 cm long) with 9 anterior region chaetigers and a characteristic brown band on the lateral side of the ventral shield and posterior side of anterior region notopodia. It inhabits irregularly curved tubes cemented to the underside of rocks. Worms may occur singly or aggregated, with up to 10 worms in a cluster. Chaetopterus aduncus sp. nov. is 8–10 cm in length, and is characterized by 10 – 11 anterior region chaetigers, characteristic J-shaped tube with one blind end, and prominent dorsal bulbous inflations in anterior region chaetigers. Chaetopterus longipes Crossland, 1904 is highly gregarious, frequently forming aggregations of hundreds of worms. It is especially common at the northern islands of Darwin and Wolf. Chaetopterus macropus Schmarda, 1861 is solitary, lives in a U-shaped tube on a sandy bottom, has 9 anterior region chaetigers and no brown bands in region-A. We compared the five Galapagos Chaetopterus species to other Pacific (Japanese and Australian) species of the genus in detail. We confirm the presence of Mesochaetopterus minutus Potts, 1914 in Galapagos, the only chaetopterid previously recorded from the archipelago. Mesochaetopterus ecuadorica sp. nov. is a large (12 – 20 cm long) solitary species with 2 middle region chaetigers, that inhabits a long, nearly straight tube with small perforations at the blind end.
New taxa: Chaetopterus galapagensis Nishi, Hickman, & Bailey-Brock, Chaetopterus charlesdarwinii Nishi, Hickman, & BaileyBrock, Chaetopterus aduncus Nishi, Hickman, & Bailey-Brock, Mesochaetopterus ecuadorica Nishi, Hickman, & Bailey-Brock