Antibiotic-resistant infections pose a growing threat to public health. Antibiotic use, regardless of whether it is warranted, is a primary factor in the development of resistance. In the United States, the majority of antibiotic health care expenditures are due to prescribing in outpatient settings. Much of this prescribing is inappropriate, with research showing that at least 30% of antibiotic use in outpatient settings is unnecessary. In this State of the Art Review article, we provide an overview of the latest research on outpatient antibiotic prescribing practices in the United States. Although many of the researchers in these studies describe antibiotic prescribing across all patient age groups, we highlight prescribing in pediatric populations when data are available. We then describe the various factors that can influence a physician's prescribing decisions and drive inappropriate antibiotic use and the potential role of behavioral science in enhancing stewardship interventions to address these drivers. Finally, we highlight the role that a wide range of health care stakeholders can play in aiding the expansion of outpatient stewardship efforts that are needed to fully address the threat of antibiotic resistance.