This study estimated national annual trends and characteristics of emergency department visits for suicide attempts and intentional self-harm in the United States from 2011 to 2020. Data were from the National Hospital Ambulatory Medical Care Survey, an annual cross-sectional national sample survey of emergency departments. Visits for suicide attempts and intentional self-harm were identified using discharge diagnosis codes (ICD-9-CM for 2011-2015; ICD-10-CM for 2016-2020) or reason-for-visit codes. The annual proportion of emergency department visits for suicide attempts and intentional self-harm was estimated. The weighted number of emergency department visits for suicide attempts and intentional self-harm increased from 1.43 million, or 0.6% of total emergency department visits, in 2011-2012 to 5.37 million, or 2.1% of total emergency department visits in 2019-2020 (average annual percent change, 19.5%, 95% CI=16.9, 22.2). Visits per capita increased from 261 to 871 visits per 100,000 persons (average annual percent change, 18.8%, 95% CI=17.6, 20.0). The increase in visits was widely distributed across sociodemographic groups. While suicide attempt and intentional self-harm visits were most common among adolescents, adults age 65 or older demonstrated the largest increase (average annual percent change, 30.2%, 95% CI=28.5, 32.0). Drug-related diagnoses were the most common co-occurring diagnosis among suicide attempt and intentional self-harm visits. Despite the rise in emergency department visits for suicide attempts and intentional self-harm, less than 16% included an evaluation by a mental health professional. A significant national increase in emergency department visits for suicide attempts and intentional self-harm occurred from 2011 to 2020, as a proportion of total emergency department visits and as visits per capita. These trends underscore an urgent need to improve the continuum of mental health care for individuals with suicidal symptoms.