Part of the firm's 'Automotive Satisfaction Report', the study is based on over 40,000 interviews yearly with Australian motorists, with 95.3 per cent of Mazda owners 'Very' or 'Fairly' satisfied with their vehicle in the 12 months leading into July 2017.
Narrowly missing out on top spot was Swedish manufacturer Volvo, with a satisfaction rate of 95.2 per cent - a decent 3.8 per cent increase on the year before.
Despite falling 2.5 per cent, Lexus maintained a top three finish, scoring 95.0 per cent satisfaction in the survey.
Meanwhile, Skoda ranked fourth (94.8 per cent, down 1.0), Isuzu Ute fifth (94.7 per cent, down 0.7), and Toyota sixth (94.6 per cent, up 0.2). Rounding out the top ten were Mercedes-Benz (94.5 per cent, up 0.2), BMW (94.4 per cent, up 3.7), Peugeot (94.3 per cent, up 4.7), and Subaru (94.3 per cent, no change).
"In such a highly competitive car market as Australia, it is critical that brands focus on their satisfaction ratings relative to their major competitors and across key segments because customer satisfaction has the potential to impact on customer retention and advocacy," said Norman Morris, director of industry communications for Roy Morgan Research.
"This research has shown that very little currently separates the satisfaction of the major players in this market, presenting a problem in how to obtain a competitive advantage on this important metric."
This survey follows a report published earlier this month by international firm J.D. Power, which claimed Hyundai customers are the happiest - although that study was specifically on initial satisfaction rather than long-term ownership.