Many astrovirus (AstV) species are associated with enteric disease, although extraintestinal manifestations in mammalian and avian hosts have also been described. In this study, the prevalence rates of porcine AstV types 1-5 (PAstV1-PAstV5) were investigated using faecal samples from 509 pigs of which 488 (95.9%) came from farms with a history of diarrhoea. All of the five known PAstV types were found to circulate in pigs in the USA, and co-infection of a single pig with two or more PAstV types was frequently observed. A high overall prevalence of 64.0% (326/509) of PAstV RNA-positive samples was detected, with 97.2% (317/326) of the PAstV RNA-positive pigs infected with PAstV4. Further genomic sequencing and characterization of the selected isolates revealed low sequence identities (49.2-89.0%) with known PAstV strains, indicating novel types or genotypes of PAstV2, PAstV4 and PAstV5. Some new features of the genomes of the PAstVs were also discovered. The first complete genome of a PAstV3 isolate was obtained and showed identities of 50.5-55.3% with mink AstV and the novel human AstVs compared with 38.4-42.7% with other PAstV types. Phylogenetic analysis revealed that PAstV1, PAstV2 and PAstV3 were more closely related to AstVs from humans and other animals than to each other, indicating past cross-species transmission and the zoonotic potential of these PAstVs.