Peter Grant Hay (9 July 1879 – 29 August 1961) was an Australian brewer, landowner, pastoralist and thoroughbred racehorse breeder. He founded the Richmond N.S. (Nathan System) Brewing Co. Ltd (Carlton & United Breweries) in Melbourne Australia. He is responsible for both the introduction of pasteurisation to Australia's dairy industry and the introduction of the Swiss Nathan System of brewing to Australia. He was the youngest of five children.