Bovine mastitis represents a major economic and welfare problem to the dairy industry worldwide, estimated to result in annual costs of €20 billion. Streptococcus uberis is a leading cause of bovine mastitis and the second most common cause in Scotland. Treatment often relies on antimicrobials, but with growing concerns over antibiotic resistance across all of human and veterinary medicine, there is a need to develop alternative treatments to preserve conventional antimicrobials. One promising approach to new antimicrobial drugs is phage therapy. Bacteriophages (phages) are naturally-occurring, free-living viruses that infect and kill bacteria. Despite promising results in human medicine, phage therapy has received limited attention for the treatment of veterinary infections. This proposal aims to identify and characterise phages active against S. uberis mastitis isolates from Scotland as validating the potential to develop phage therapy against this important dairy cow pathogen and as a route to preserving effective therapies.