This manuscript is under review (first submitted for publication in August, 2020; first revision submitted in March, 2021, second revision submitted in May, 2021; accepted in *Psychological Bulletin* in June, 2021). All files in this repository are licenced under the terms and conditions of the Creative Commons CC-BY 4.0 license. **Abstract** Judged by the sheer amount of global media coverage, loneliness rates seem to be an increasingly urgent societal concern. From the late 1970s onward, the life experiences of emerging adults have been changing massively due to societal developments such as increased fragmentation of social relationships, greater mobility opportunities, and changes in communication due to technological innovations. These societal developments might have coincided with an increase in loneliness in emerging adults. In the present preregistered cross-temporal meta-analysis, we examine whether loneliness levels in emerging adults have changed over the last 43 years. Our analysis is based on 449 means from 345 studies with 437 independent samples and a total of 124,855 emerging adults who completed the UCLA loneliness scale between 1976 and 2019. Averaged across all studies, loneliness levels linearly increased with increasing calendar year (beta = 0.224, 95% CI [0.138, 0.309]). This increase corresponds to 0.56 standard deviations on the UCLA loneliness scale over the 43-year period of study. Overall, the results imply that loneliness can be a rising concern in emerging adulthood. Although the frequently-used term “loneliness epidemic” seems exaggerated, emerging adults should therefore not be overlooked when designing interventions against loneliness. **File Directory** Pre-Registration (blind): https://osf.io/eu3c7/?view_only=9ada6220ef0a4bfdb6e659aa9b6cfb53