Background: Unwanted loneliness is a growing public health concern among older adults, with documented negative effects on mental and physical health. Despite its relevance, little evidence exists regarding its prevalence and associated factors in rural southern Spain. This project, funded by the Provincial Council of Jaén (Spain) through Resolution No. 295 of August 19, 2025, investigates unwanted loneliness in older adults, focusing on risk and protective factors through an in-depth analysis in the province of Jaén. Objectives: This study aimed to evaluate the prevalence of unwanted loneliness among individuals aged 60 and over in Jaén and to identify sociodemographic, family, and psychosocial risk and protective factors. Methods: An analytical, cross-sectional, observational study was conducted with approximately 429 older adults recruited from community and residential centers in urban and rural areas of Jaén. Loneliness was assessed using the De Jong-Gierveld Loneliness Scale, while complementary instruments measured depression, resilience, and perceived social support. Sociodemographic and mobility data were also collected. Statistical analyses included descriptive statistics, Spearman correlations, regression models, and non-parametric tests. Results: A high prevalence of moderate and severe unwanted loneliness was found, particularly among single, widowed, or those living without a partner. Protective factors included having children, greater social support, and resilience. Depressive symptoms were a significant risk factor. Loneliness was also associated with limited mobility, poor physical or mental health, financial difficulties, and loss of loved ones. Social and environmental factors, such as living alone, geographic isolation, lack of transportation, or weak support networks, further increased risk. Conclusions: The study revealed a high prevalence of unwanted loneliness among older adults in rural southern Spain, particularly linked to living without a partner, widowhood, and poor health. Findings underscore the urgent need for targeted interventions to strengthen protective resources, reduce risks, and design community and health strategies adapted to older adults.