Leptospirosis is a human and veterinary illness caused by spirochetebacteriain thegenusLeptospira. In symptomatic infection the clinical presentation ranges from non-specific febrile illness to fulminant organ system failure with a high case fatality rate. Leptospires are excreted in the urine of infected mammals with rodents being the main source for human exposures. Leptospires can survive for months in urine-contaminated water and moist soil and humans can acquire infection via direct exposure to urine from infected animals or indirectly though contact with urine-contaminated water and wet soil. While leptospirosis occurs worldwide, it is more common in tropical and sub-tropical climates where it is estimated to cause more than a million illnesses and result in almost 60 000 deaths annually. Floodrelated leptospirosis outbreaks have been documented in many settings, including Australia, and are expected to increase with climate change. The largest outbreak of human leptospirosis in Australia occurred in 2018 when 84 cases where identified among workers on a berry farm in New South Wales. In 2019 unprecedented clusters of fatal canine leptospirosis occurred in urban areas of Sydney and Melbourne. It is not yet known whether the recent leptospirosis outbreaks among dogs and humans are an aberration or herald a growing threat to public and veterinary health in Australia. A One Health approach is critical to understanding the emergence of leptospirosis in an era of climate change, population growth, changes to agricultural practices, increased travel and urbanisation, both in Australia and abroad.