Eilish Billie Sagittarius-born Pirate Baird O'Connell was born on December 18, 2001, in Los Angeles' Highland Park neighborhood. She was eight years old when she enrolled in the Los Angeles Children's Choirs. She was raised in a family of musicians and actors.

She began writing songs at the age of 11, with the help of her older brother Finneas O'Connell. Her first song, which was originally composed by her brother Ocean Eyes, was recorded in October 2015. In 2016, the song was made available on Soundcloud as a single along with a video. The extremely young artist receives his or her first compliments.

The performer has made a name for herself as one of generation Z's biggest stars since releasing her debut album. She released a number of songs in 2020, including Tomorrow and Therefore I Am, and her second album Happier than Ever, which was less well-received by reviewers than her first, was released in 2021.