OBJECTIVE: This study aimed to estimate population-level prevalence of obesity and severe obesity for New York City youth and examine the most recent trends over time. METHODS: All public school youth in grades kindergarten through eighth (K-8) (2011-2012 through 2016-2017) with valid weight and height measures were included (N = 1,137,782 unique students; 3,720,297 observations). Age- and sex-specific BMI percentiles for obesity and severe obesity were estimated using Centers for Disease Control and Prevention growth charts. Repeated cross-sectional analyses were conducted using logistic regression, weighting for missing or invalid responses and accounting for clustering by students and schools to examine trends over time and by sociodemographics. RESULTS: Among youth in K-8 (aged 5-15 years, 48.8% girls), the prevalence of obesity and severe obesity in 2011-2012 was 21.5% and 6.4%, respectively, compared with 20.2% and 6.0%, respectively, in 2016-2017. Since 2011-2012, decreasing trends in obesity and severe obesity (relative declines: 6.0% and 6.3%, respectively, P < 0.001) have been observed. Significant decreases were observed for all subgroups (P < 0.001), although there remained disparities in relative declines over time by race/ethnicity and poverty. CONCLUSIONS: Decreasing trends in obesity and severe obesity among all New York City K-8 public school youth are promising; however, persistent disparities highlight the need to improve intervention design and implementation strategies for groups disproportionately burdened by obesity.