Those behind the award said Portman was seriously involved with important social and environmental programmes.
They include the Tacare Girl's Scholarship Programme of the Jane Goodall Institute, a non-profit organisation that carries out wildlife research in Tanzania.
The programme was established to address limited opportunities for women's education.
It provides access to secondary and higher education, leading to job opportunities.
Portman's prize is 50,000 US dollars and a trophy. The cash she receives is being donated to the programme, organisers said.
Academy Award-winning Italian set designer Dante Ferretti, who worked on The Aviator and Sweeney Todd, was named as the recipient of the "star of the year" award.
The prizes were being awarded at the Kineo Italian Movie Awards in Venice.
