Jarkko Santeri Lahti (born 1978) is a Finnish actor. He is best known for his role as Olli Mäki in the film The Happiest Day in the Life of Olli Mäki (2016), for which he received the Jussi Award for Best Actor. Lahti has also appeared in films Sparrows (2015), The Unknown Soldier (2017), Helene (2020) and The Woodcutter Story (2022).