Preonzo was a municipality of the district Bellinzona in the canton of Ticino in Switzerland.
On 2 April 2017, the former municipalities of Camorino, Claro, Giubiasco, Gnosca, Gorduno, Gudo, Moleno, Monte Carasso, Pianezzo, Preonzo, Sant'Antonio and Sementina merged into the municipality of Bellinzona.