Background: This study aimed to identify patterns of overall, team, and individual sport participation and examine the prospective associations between these patterns and loneliness in young people. Methods: We analyzed data from 4241 young people, from waves 3 (8–9 y) to 9 (20–21 y) of the Longitudinal Study of Australian Children. We conducted latent class analyses to identify overall and team versus individual sport participation trajectories and used adjusted log-Poisson regression models to examine the associations between these trajectories and loneliness at wave 9. Results: Latent class analyses identified 4 distinct overall sport participation classes which were labeled: nonparticipants (24%), dropouts (42%), initiators (7%), and consistent participants (27%). Compared with nonparticipants, consistent participants had a lower risk of loneliness (risk ratios = 0.69; 95% CIs, 0.59–0.81). Latent class analyses also identified 4 distinct team versus individual sport participation classes: team and individual sport nonparticipants (38%), individual sport participants (14%), moderate team sport participants (14%), and high team sport participants (34%). Compared with the team and individual sport nonparticipants, the high team sports participants had a lower risk of loneliness (risk ratios = 0.70; 95% CIs, 0.53–0.92). Conclusions: Young people who continued participating in sport in general, and particularly in team sport, had a reduced risk of loneliness. Continued participation in sports should be promoted to improve a range of physical, mental, and social health benefits. Furthermore, team-based sport can provide additional health and well-being benefits, including reduced loneliness due to the group nature of participation.