The US sitcom How I Met Your Mother premiered on CBS on September 19, 2005. Created by Craig Thomas and Carter Bays, the show is presented from the perspective of Ted Mosby in 2030 ("Future Ted") as he tells his children how he met the titular mother. The show lasted for nine seasons and 208 episodes; the finale first aired on March 31, 2014. A stand-alone sequel series, How I Met Your Father, premiered on Hulu on January 18, 2022. Created by Isaac Aptaker and Elizabeth Berger, the show is presented from the perspective of Sophie in 2050 as she recounts to her unseen son the events that followed meeting his father in January 2022.

The main characters of How I Met Your Mother are: Ted Mosby, a romantic searching for "The One"; Barney Stinson, a womanizer; Robin Scherbatsky, a journalist who moved to New York in 2005; and Marshall Eriksen and Lily Aldrin, a long-term couple. Although the show is based around The Mother, her first appearance is not until the season eight finale. How I Met Your Father meanwhile features the main characters Sophie, a romantic searching for her "soulmate"; Jesse, an aspiring musician; Sid, Jesse's best friend; Valentina and Charlie, Sophie's best friend and her British boyfriend; and Ellen, Jesse's adoptive sister, while also featuring main characters from How I Met Your Mother in guest roles.

Many of the main characters' relatives appear throughout the show, such as Lily's father or Barney's brother. They may also be seen in family gatherings, such as Barney and Robin's wedding or Marshall's father's funeral. Ted's children and Marvin W. Eriksen (son of Marshall and Lily) appear in the background of many episodes and key moments without being crucial to many plots.

Ranjit, Carl, and several other characters often appear because they work in places the main cast frequently visit/hang out at (such as MacLaren's Pub). Characters in relationships with Ted, Barney, or Robin often appear in several episodes within a short period of time, such as Victoria, Nora, or Kevin. Minor characters such as the Slutty Pumpkin or Mary the Paralegal may only appear in one or two episodes, but still play a crucial role in the episodes in which they appear.