Prelateral merger of /e/ and /æ/ is a salient acoustic feature of speech from Melbourne and the state of Victoria in Australia, but little is known about its presence in other parts of the country. In this study, automated methods of data collection, forced alignment, and formant extraction are used to analyze the regional distribution of the vowel merger within all of Australia, in 4.3 million vowel tokens from naturalistic speech in 252 locations. The extent of the merger is quantified using the difference in Bhattacharyya’s distance scores based on phonetic context, and the regional distribution is assessed using spatial autocorrelation. The principal findings are that the merger is most prominent in Victoria and least prominent in Sydney and New South Wales. We also find preliminary indications that it may be present in other parts of the country.