To what degree do self-ratings of loneliness converge with informant ratings? In this study, we obtained self-ratings of loneliness from 463 young adults and informant ratings from their parents, friends, and romantic partners. Convergence among these ratings was estimated using structural equation models for multitrait-multimethod data and compared to self-informant convergence of life-satisfaction ratings. Self- and informant ratings were moderately correlated and comparable to self-informant correlations obtained for life satisfaction. Romantic partners were more accurate in their judgments than both friends and parents, who did not differ significantly from each other in terms of accuracy. Together, these findings indicate that informant ratings of loneliness can be used as valid indicators of loneliness in applied contexts and in future research.