The purpose of this study was to determine the key determinants of loneliness of older Canadians. We drew on the assumptions concerning the importance of person-environment fit to test the relative importance of personal characteristics, deprived living conditions, social network/social engagement, and satisfaction in explaining loneliness. Data comprised a sample of 3,799 respondents over age 65 drawn from Statistics Canada’s General Social Survey, Cycle 22. Personal characteristics, social network size and composition, and satisfaction with network contact were found to be related to loneliness, as were indicators of living in economically and socially challenging conditions. Older adults who had experienced a recent downturn in their financial situation, and who lacked the help needed to cope with a recent personal challenge, reported higher levels of loneliness. A striking feature of our findings is the relatively low scores on loneliness of older Canadians compared to older adults in other countries.