The Most Serene Republic is a Canadian indie rock band formed in Milton, Ontario, by band members Adrian Jewett, Ryan Lenssen, and Nick Greaves, who had all left school to pursue more artistic ventures. The band takes its name from the sobriquet of formerly independent Venice under the Doges, which was regarded as "The Most Serene Republic of Venice."

The Most Serene Republic released its debut album, Underwater Cinematographer, in 2005 on the Arts & Crafts label. They are the first band on the A&C label that isn't related in one way or another to Broken Social Scene (though Ryan and Adrian perform sometimes in their live shows). They later released a tour EP in spring/summer of 2006, titled Phages, capturing more of the sweep of their live performances.

Originally formed in mid-2003 as a duo (Lenssen and Jewett) known as Thee Oneironauts (O-nye-rawn-nauts). The pair would quickly record and self-release an EP entitled Night of the Lawnchairs on Lenssen's GROK Studios imprint. The Oneironauts grew to trio status with the addition of Greaves on keyboard and guitar.

Their live shows are known for being extremely entertaining, and intense with dancing, and cramming so many sounds to overload the senses.