Background Ticagrelor and prasugrel are potent P2Y12 inhibitors with superior efficacy compared with clopidogrel among patients with ST-segment-elevation myocardial infarction (STEMI), though use in recent practice is not well described. In this retrospective study, we assessed trends, predictors, and variation in use of P2Y12 inhibitors in patients with STEMI in the United States. Methods and Results We identified 169 505 STEMI patients in the Chest Pain-Myocardial Infarction Registry from October 2013 through March 2017. We determined national utilization rates of P2Y12 inhibitors at discharge, patient predictors for each medication, and variation in use between hospitals. In a subset of 9655 Medicare patients ≥65 years old, we compared 1-year adjusted risks of death, myocardial infarction, stroke, and bleeding based on hospital quartile of potent P2Y12 inhibitor use. Rates of ticagrelor use increased from 18.0% to 44.0%, while rates of prasugrel and clopidogrel use decreased from 24.6% to 13.5% and 57.4% to 42.6%, respectively. Prior percutaneous coronary intervention was the strongest clinical predictor for use of ticagrelor (adjusted odds ratio, 1.13 [95% CI, 1.09-1.18]) and prasugrel (adjusted odds ratio, 1.27 [95% CI, 1.21-1.34]) compared with clopidogrel. Predictors of clopidogrel use included no insurance, insurance with Medicare or Medicaid, and features associated with higher bleeding risk. The median hospital usage rate for newer P2Y12 inhibitors was 51.3% (interquartile range, 35.0%-65.9%), with substantial variation between hospitals (adjusted median odds ratio, 2.92 [95% CI, 2.77-3.10]). Among patients ≥65 years old, there were no differences in adjusted 1-year risks of adverse outcomes across hospital quartiles of potent P2Y12 inhibitor use. Conclusions Almost one-half of STEMI patients by 2017 were discharged on ticagrelor while far fewer received prasugrel. Patient characteristics are associated with P2Y12 inhibitor selection, though substantial hospital variation exists. Identifying barriers to use of more potent P2Y12 inhibitors may improve patient-centered decision-making for STEMI patients.