Seidi Helena Alexandra Haarla (born January 1, 1984) is a Finnish actress. She played the female lead in Juho Kuosmanen's film Compartment No. 6 (2021). She won the European Film Promotion (EFP) Shooting Stars Award for her role as one of the most promising film actors of the year.

Haarla was born in 1984 in Kirkkonummi in southern Finland. She comes from a family of actors and artists. Her father is artist Teuri Haarla (* 1955). Her younger sister Ruusu Haarla (* 1989) is a playwright and director. Her grandparents were actor Saulo Haarla (1930–1971) and soprano and actress Helena Salonius (1930–2012); her great-grandparents include stage actress Tyyne Haarla (1892–1968) and writer Lauri Haarla (1890–1944).