Olivia Bouyssou (born 25 February 1982), known professionally as Olivia Merilahti and Prudence, is a Finnish-French singer and composer, best known for being the frontwoman of the musical duo The Dø. Her work has been compared to that of Björk, whom she cites as a major influence. Merilahti was born to a French father and a Finnish mother. She primarily uses English in music, which she learned at an early age.

Finnish is my intimate language; I speak Finnish with my mum and I've been living in France for most of my life, so it's been my secret language. My secret weapon somehow. So these different languages play different roles in my life, and English has always been the musical one.

Having studied classical music in Helsinki, Merilahti gravitated to rock music, then jazz and electronic music. In 2004, during the writing of music from the movie Empire of the Wolves, she met Dan Levy, with whom she formed French indie rock band The Dø. In 2020, she released a solo project under the name Prudence.