Suicide is the second leading cause of death among high school-aged youths 14–18 years after unintentional injuries. This report summarizes data regarding suicidal ideation (i.e., seriously considered suicide) and behaviors (i.e., made a suicide plan, attempted suicide, and made a suicide attempt requiring medical treatment) from CDC’s 2019 Youth Risk Behavior Survey. Results are reported overall and by sex, grade, race/ethnicity, sexual identity, and sex of sexual contacts, overall and within sex groups. Trends in suicide attempts during 2009–2019 are also reported by sex, race/ethnicity, and grade. During 2009–2019, prevalence of suicide attempts increased overall and among female, non-Hispanic white, non-Hispanic black, and 12th-grade students. Data from 2019 reflect substantial differences by demographics regarding suicidal ideation and behaviors. For example, during 2019, a total of 18.8% of students reported having seriously considered suicide, with prevalence estimates highest among females (24.1%); white non-Hispanic students (19.1%); students who reported having sex with persons of the same sex or with both sexes (54.2%); and students who identified as lesbian, gay, or bisexual (46.8%). Among all students, 8.9% reported having attempted suicide, with prevalence estimates highest among females (11.0%); black non-Hispanic students (11.8%); students who reported having sex with persons of the same sex or with both sexes (30.3%); and students who identified as lesbian, gay, or bisexual (23.4%). Comprehensive suicide prevention can address these differences and reduce prevalence of suicidal ideation and behaviors by implementing programs, practices, and policies that prevent suicide (e.g., parenting programs), supporting persons currently at risk (e.g., psychotherapy), preventing reattempts (e.g., emergency department follow-up), and attending to persons who have lost a friend or loved one to suicide.