A choreographer and dancer, Sieni founded the Compagnia Parco Butterfly in 1983 and the Compagnia Virgilio Sieni in 1992, emerging as one of the leading figures of the European contemporary scene.
He created new shows for the most important Italian cultural organizations and was awarded a number of prizes (Ubu, Danza&Danza, Lo Straniero, and Anct). In 2013 he was appointed director of the Dance section of the Biennale di Venezia (until December 2016) and was nominated Chevalier de l’ordres des arts et de lettres by the French Ministry of Culture.
He represented Italy both in Marseille - European Capital of Culture in 2013, with the project "The art of gesture in the Mediterranean" that involved 160 performers from many different countries, and in Brussels as part of the six-month period of the Italian Presidency of the European Union 2014 with his project, Vita Nova. In 2015 he made Atlante del Gesto for the Fondazione Prada in Milan.