Bat For Lashes, The Horrors, Glasvegas and Friendly Fires are also on this year's list, which is voted for by a panel of critics and music industry workers.
The winner, which will be announced on September 8, takes home a £20,000 prize.
The list of contenders features the usual eclectic mix of acts with eccentric Jazz quintet Led Bib, art-rockers The Invisible and folk act Sweet Billy Pilgrim among the more unusual nominations.
Florence and the Machine and Kasabian have been installed as the early bookmakers' favourites by William Hill, with Sweet Billy Pilgrim as the 10/1 outsiders.
Doves (Kingdom Of Rust) and Lily Allen (It's Not Me, It's You), who were hotly tipped to make the list, miss out.
Previous winners have included Arctic Monkeys, Dizzee Rascal, M People, Gomez and Franz Ferdinand. Manchester rock act Elbow took home the gong last year for their Seldom Seen Kid LP.
The full list of 2009 Mercury Prize nominations are (click where possible for reviews):
- Bat For Lashes: Two Suns
- Friendly Fires: Friendly Fires
- Florence and the Machine: Lungs
- Glasvegas: Glasvegas
- Lisa Hannigan: Sea Shew
- The Horrors: Primary Colours
- The Invisible: Invisible
- Kasabian: West Ryder Pauper Lunatic Asylum
- La Roux: La Roux
- Led Bib: Sensible Shoes
- Speech Debelle: Speech Therapy
- Sweet Billy Pilgrim: Twice Born Men