Shareholders backed a slate of eight candidates submitted by Italy's Treasury, the leading investor in Leonardo with a 30.2% stake, including Cingolani and former NATO ambassador to Afghanistan Stefano Pontecorvo, who was appointed chairman.

A Leonardo source said the new board was set to meet later on Tuesday to formalise the appointment of Cingolani, 61, who has no experience at the top of a listed company.

In an unusual move, the remaining four board members were elected from a list submitted by U.S. investment firm GreenWood Investors and hedge fund Sachem Head, while a rival list from Italian institutional investors' club Assogestioni was defeated.

"Sachem Head supports the company's current strategy and believes that the newly elected board has the right mix of skills and experience to surface significant shareholder value at Leonardo," the founder and portfolio manager of the hedge fund Scott Ferguson told Reuters.

"We believe that the company will emerge as a true European Aerospace & Defense champion in the coming years," he added.

Leonardo has benefited from rising government spending on defence in the wake of the Ukraine war, but has been less profitable than competitors such as Germany's Rheinmetall or Britain's BAE Systems.

Cingolani, who has a background as a physicist and was previously Leonardo's chief technology and innovation officer, has informally advised Italian Prime Minister Giorgia Meloni on energy policy in recent months.

He succeeds former banker Alessandro Profumo, who had been Leonardo's chief executive for six years.

Sources told Reuters that Cingolani will take the additional role of director general, while the head of the Italian unit of European missile maker MBDA Lorenzo Mariani will return to Leonardo as co-director general.

(Reporting by Alvise Armellini, additional reporting by Svea Herbst-Bayliss, editing by Alexander Smith)