Objective: To forecast the prevalence and direct health care costs of osteoarthritis (OA) and rheumatoid arthritis (RA) in Australia to the year 2030. Methods: An epidemiologic model of the Australian population was developed. Data on the national prevalence of OA and RA were obtained from the Australian Bureau of Statistics (ABS) 2014–2015 National Health Survey. Future prevalence was estimated using ABS population projections for 2020, 2025, and 2030. Available government data on direct health care expenditure for OA and RA were modeled to forecast costs (in Australian $) for the years 2020, 2025, and 2030, from the perspective of the Australian public health care system. Results: The number of people with OA is expected to increase nationally from almost 2.2 million in 2015 to almost 3.1 million Australians in 2030. The number of people with RA is projected to increase from 422,309 in 2015 to 579,915 in 2030. Health care costs for OA were estimated to be over $2.1 billion in 2015; by the year 2030, these are forecast to exceed $2.9 billion ($970 for every person with the condition). Health care costs for RA were estimated to be over $550 million in 2015, including $273 million spent on biologic disease-modifying antirheumatic drugs. Health care costs for RA are projected to rise to over $755 million by the year 2030. Conclusion: OA and RA are costly conditions that will impose an increasing health care burden at the population level. These projections provide tangible data that can be used to map future health service provision to expected need.