Orso II Participazio (died 932) was the eighteenth doge of the Republic of Venice, by tradition (historically, he was the sixteenth), from 912 to 932.

In 912 he was kidnapped in the Adriatic by a Serb prince of Zachlumia by the name of Mihailo Višević while returning with the Doge's son from an official visit to Constantinople.

(There was a prior Orso II Participazio who vied for dogeship in about 887 but appears to have been entirely unrelated.)

As soon as elected, he sent his son Pietro to Constantinople in order to re-establish the relationships with the Byzantine emperor, which his predecessors had neglected.

In 932, he withdrew to the monastery of Saint Felice in Ammiana, where he led a monastic life until his death.