The Swell Season is a musical duo formed of Irish musician Glen Hansard and Czech singer and pianist Marketa Irglova.

The Swell Season name is derived from Hansard's favourite novel by Josef Škvorecký from 1975 bearing the same title.

Having met in the Czech Republic whilst Hansard was on tour there with his band The Frames he invited Markéta on stage to perform with the band. There followed musical collaborations and an album release. They both rose in prominence after starring in the 2007 film Once, from the soundtrack to which their song Falling Slowly was nominated for the 2007 Grammy for Best Song Written for Motion Picture and won them the 2007 Academy Award for Best Original Song.

Life eventually reflected art as they became a romantic couple off-screen, but this relationship ended in 2009 - though they continue to write, record and perform together.