Objective: Loneliness is an important health problem in rural areas of Japan because of its ageing and declining population. Therefore, we investigated the association between loneliness and health. Materials and Methods: Self-administered questionnaires were distributed to rural adult residents. The Japanese 3-item versions of the UCLA Loneliness Scale, self-rated health (SRH), and objective health status (whether the respondents had a physical and/or mental illness) were used. We defined a UCLA score of four points or more as loneliness, an SRH of four points or more as a subjective healthy state, and no physical or mental illness as an objective healthy state. The association was adjusted for sociodemographic data, lifestyle habits, and isolation risk using logistic regression analysis. Results: The five-year population decline rate in the target areas was 10.2 to 12.3%. Of the 2,700 participants, there were 1,211 male and 1,489 female respondents, with an average age of 65.4 years. Moreover, 358 (13.6%) were living alone, and 829 (31.5%) were living in couple-only households. Among the participants, 1,395 (53.2%) experienced loneliness, 1,751 (65.7%) had good self-rated health, and 1,587 (60.8%) had objective health status. Loneliness was negatively associated with good SRH (OR=0.56, CI=0.45-0.70) and objective health status (OR=0.57, CI=0.46-0.71) after adjusting for sociodemographic data, lifestyle habits, and the risk of isolation. Statistically significant confounding factors for subjective and/or objective health status were employment, not smoking, obesity, exercise, having a family doctor, having an above-average number of teeth, and the ability to leave home. Conclusion: In an ageing and declining population, loneliness is an independent factor affecting the health status of rural residents and is not limited to older adults. Therefore, measures to reduce it are needed.