Previous work shows that emergency medicine attending physicians have higher-than-average rates of burnout. Preliminary data suggest that emergency medicine residents are also at risk for burnout. The objective of this study was to conduct the first national survey assessment of US emergency medicine residents to determine the prevalence of burnout. This prospective 2017 National Emergency Medicine Resident Wellness Survey study was conducted through the Wellness Think Tank, whereby emergency medicine residents from 247 residencies across the United States were invited to participate in a national survey. The primary measure of burnout was the Maslach Burnout Inventory–Human Services Survey. In accordance with others' work, "burnout" was defined as a dichotomous variable represented by high levels of emotional exhaustion or depersonalization. Because of interpretative variability with the survey tool, we also calculated burnout rates by using a more restrictive definition and a more inclusive definition that have been reported in the literature. Surveys were completed by 1,522 residents (21.1% of all US emergency medicine residents), representing 193 of 247 US emergency medicine residency programs (78.1%). Within this sample, the prevalence of burnout was 76.1% (95% confidence interval 74.0% to 78.3%). With alternative definitions applied, burnout prevalence rates for this same sample were 18.2% (95% confidence interval 16.3% to 20.1%) with the more restrictive definition and 80.9% (95% confidence interval 78.9% to 82.9%) with the more inclusive definition. The majority of US emergency medicine residents responding to this survey reported symptoms consistent with burnout, highlighting that physician burnout in the emergency medicine profession seems to begin as early as residency training. These findings may provide a baseline against which future work can be compared.