Finneas Baird O'Connell (born July 30, 1997), known mononymously as Finneas (stylized in all caps), is an American singer-songwriter, record producer, and actor. He has written and produced music for various artists, most notably his sister, Billie Eilish. He has won eight Grammy Awards among 13 total nominations, including nominations for the Big Four categories. He has made history as the youngest act to win the Producer of the Year, Non-Classical category. For his work with Eilish, he has won Record of the Year twice in a row, Album of the Year, Song of the Year, Best Pop Vocal Album, and Best Engineered Album, Non-Classical. He was also nominated for Best New Artist for his solo work. Their song "No Time to Die" from the film of the same name earned him an Academy Award, a Golden Globe and another Grammy.

Finneas has released several singles as a solo artist, and his debut EP, Blood Harmony, was released in October 2019. The EP includes "Let's Fall in Love for the Night", his most successful song to date, peaking at number 17 on the US Billboard Alternative Songs chart. His debut studio album Optimist was released through Interscope Records in October 2021.

Finneas starred in the 2013 independent film Life Inside Out. He is also known for his role as Alistair in the Fox musical comedy-drama series Glee. He has also made an appearance on the American sitcom Modern Family.