Research seems to support loneliness as a risk factor for mental health problems in the elderly. Most studies analyzing the effects of loneliness on older adults' mental health have relied on convenience samples. In this study, the prevalence and predictors of feelings of loneliness were studied in a representative sample of 272 community-dwelling Spanish older adults. The potential of feelings of loneliness to significantly contribute to the explanation of mental health of the elderly was also explored. The percentage of people reporting feelings of loneliness was 23.1%. Being a woman, being older, living alone, having fewer economic resources, having lower perceived health, and being dissatisfied with the frequency of contact with relatives and friends were found to be significant predictors of feelings of loneliness. Loneliness contributed significantly to the explanation of mental health, even when other significant variables were statistically controlled. The results of this study suggest that loneliness is a relevant factor for the analysis and understanding of mental health in the elderly.