The list includes five from the UK and one American author, Tania James, for her novel The Tusk that Did the Damage.
Poet Andrew McMillan's Physical won The Guardian First Book Award last year.
The Swansea University-backed award will go to the best published literary work in English, written by an author aged 39 or under.
Chair of the judges Prof Dai Smith called the works "eye-catching, eclectic and totally energising".
The shortlisted writers are:
A set of short stories set in Caerphilly by locally-born writer Thomas Morris was on the long list but did not make the final cut.
The winner will be announced at a gala ceremony at Swansea University, which sponsors the prize, on International Dylan Thomas Day, 14 May.
The shortlist for the £30,000 Dylan Thomas Prize for young writers has been unveiled.