Ovine GM1-gangliosidosis is an autosomal recessive lysosomal storage disorder found in sheep. Affected lambs are born relatively normal but begin exhibiting severe neurological symptoms at approximately 4 months of age. Pathology progresses rapidly in affected lambs, ultimately resulting in euthanasia or death by 5 to 6 months. In humans, mutations in the β-galactosidase (GLB1) gene are responsible for similar phenotypes. Non-functional β-galactosidase results in a buildup of GM1 ganglioside and other terminal linked galactose containing molecules in the brain and visceral tissues. Using the Illumina® OvineSNP50 BeadChip, seven affected and ten unaffected animals were genotyped and a genome wide association analysis was performed using PLINK. A significant association was detected for a region on OVA19; further investigation showed the region was orthologous to HSA3 containing GLB1. Sequence analysis showed a G to T base pair substitution mutation in exon 6 of ovine GLB1 causing a cysteine to phenylalanine amino acid substitution. A PCR-RFLP assay using AciI restriction enzyme was designed for genotyping lambs. To date, 1038 animals have been genotyped using the DNA-based assay and all affected lambs have been shown to be homozygous for the mutation. Conversely, individuals with normal phenotypes were either heterozygous or homozygous for the alternative allele. Affected lambs will be used to further explore the disease and therapies for humans and heterozygotes will be used to continue to produce said affected lambs. Animal models for human diseases like ovine GM1-gangliosidosis can further the medical field and make research possible that otherwise would not be completed.