Astroviruses are recognized as a leading cause of gastroenteritis in humans and animals. They are also associated with extra-intestinal diseases, such as hepatitis in ducklings, nephritis in chickens, and encephalitis in cattle. In February 2017, a fatal infection of goslings characterized by visceral urate deposition was reported in the Shandong province, China. Our systematic investigation led to the isolation of an astrovirus, designated AAstV/Goose/CHN/2017/SD01, and similar disease was reproduced by experimental infection of healthy goslings, fulfilling Koch's postulates. The isolated astrovirus replicated well and resulted in 100% mortality of goose embryos. Complete genome sequence analysis revealed that the isolate was genetically distinct from known astroviruses and closely related to members of the avastrovirus genogroup II. Experimental infection showed that the isolate was highly pathogenic in goslings, causing clinical signs, growth repression and in many cases mortality. Histopathological examination indicated that lesions occurred mainly in the kidneys of infected birds. However, virus-specific genomic RNA was detected in all representative tissues, and virus shedding was detected up to 12 days after inoculation, suggesting that the isolate was able to spread systemically and replicate efficiently in vivo. Collectively, our study demonstrates, for the first time, the etiological role of a genetically distinct astrovirus in the fatal infection of goslings.