"Annelida Polychaeta V" constitutes a new advance in the knowledge of the Polychaetous Annelids of the coasts of the Iberian Peninsula and the Balearic Islands. The current volume comprises a detailed study of the families Aberrantidae, Arenicolidae, Calamyzidae, Stauronereidae, Fauveliopsidae, Ichthyotomidae, Lumbrineridae, Maldanidae, Myzostomidae, Oenonidae, Parergodrilidae, as well as pelagic (Alciopidae, Iospilidae, Lopadorrhynchidae, Tomopteridae and Typhloscolecidae) and meiofaunal families (Dinophilidae, Diurodrilidae, Polygordiidae, Protodrilidae, Protodriloididae and Saccocirridae), the exception being Nerillidae, that was already addressed in an earlier volume. To achieve this, an in-depth taxonomic and bibliographic review of each family is accomplished, presenting a general introduction, including the most relevant features on their taxonomy, anatomy and systematics, along with identification keys for genera and species. For each of the 158 species covered in this volume, the reader will find a detailed description, presenting their most diagnostic morphological characters, together with illustrations and a summary of the state-of-the-art on their biology and geographical distribution. This volume follows on the four previous books on Polychaetes in the Fauna Ibérica series: Volumes 21 (San Martín, 2003), 25 (Viéitez et al., 2004), 36 (Parapar et al., 2012) and 41 (Parapar et al. , 2015), thus almost finishing the review of the clade Aciculata, and continuing the study of the Sedentary Polychaetes, ending the clade Scolecida and continuing the clade Canalipalpata.