13 Reasons Why (also stylized as TH1RTEEN R3ASONS WHY) is an American teen drama television series based on the 2007 novel Thirteen Reasons Why by author Jay Asher. Developed for Netflix by Brian Yorkey and with Selena Gomez serving as an executive producer, the series stars Dylan Minnette and Katherine Langford alongside an ensemble cast. The series follows the students of the fictional Liberty High School and the wide range of social issues affecting modern youth.

The show originally revolved around Clay Jensen (Minnette) and the aftermath of the suicide of fellow student Hannah Baker (Langford). Before her death, she leaves behind a box of cassette tapes in which she details the reasons why she chose to kill herself as well as the people she believes are responsible for her death.

The first season was released on Netflix on March 31, 2017. It became the second most watched series on Netflix at the time of its release. Netflix renewed 13 Reasons Why for a second season due to the success of the initial 13 episodes; the second season was released on May 18, 2018. A third season was released on August 23, 2019; that same month, the series was renewed for a fourth and final season, which was released on June 5, 2020.

13 Reasons Why received mixed reviews. The first season received positive reviews from critics and audiences, who praised its themes, emotional weight, subject matter, character development and acting, particularly the performances of Minnette and Langford. However, it prompted concerns from mental health professionals due to its graphic depiction of issues such as suicide, sexual assault, and bullying, along with other mature content. In response, Netflix added a warning card in March 2018 that plays at the start of each episode warning viewers about the themes of each season. In July 2019, Netflix edited out the suicide scene in the first-season finale. The later three seasons received negative critical response. Coinciding with the release of the second season, Netflix released a video with the cast that cautioned viewers about some of the topics covered in the show and provided a support website with crisis numbers for people affected by depression, anxiety and other mental health issues. For her performance, Langford received a Golden Globe Award nomination for Best Actress – Television Series Drama.