Following are key details of the deal:

** The merged group to have annual sales of 7.9 million vehicles and generate recurring operating profit of almost 10 billion euros ($12 billion) on revenue of 180 billion euros, based on aggregated 2019 results.

** Aim to complete the merger in the first quarter of 2021.

** FCA and PSA gained European Union antitrust approval for their merger in December, after pledging to boost Japanese rival Toyota Motor.

** PSA Chief Executive and future Stellantis CEO Carlos Tavares said all regulatory approvals had been obtained.

** The new group to be domiciled in the Netherlands, with listings in Paris, Milan and New York.

** Once completed, the merger is expected to generate more than 5 billion euros in annual synergies. The two groups say no plants would be closed.

** To unite brands such as Fiat, Jeep, Dodge, Ram Alfa Romeo and Maserati with Peugeot, Citroen, Opel and DS.

** Tavares to be the group's CEO for an initial five-year term. FCA Chairman John Elkann to become chairman.

** The merged group to have 11 board members including Tavares, five nominated by PSA and five by FCA.

** FCA CEO Mike Manley to head the American operations of Stellantis.

** FCA and PSA signed a binding tie-up agreement in December 2019, which was amended in September last year to reflect a change in conditions as a result of the COVID-19 pandemic.

** Prior to completion, FCA to pay its shareholders a 2.9 billion euro special dividend. That was cut from an original 5.5 billion euros to preserve cash because of the coronavirus crisis. PSA has said it would postpone the planned spin-off of its 46% stake in parts maker Faurecia until after the merger's closing and extend it to all shareholders.

** Based on performance, market conditions and outlook, the boards of both FCA and PSA will consider a potential 500 million euro dividend to shareholders of each company before the closing of the merger or, alternatively, a one billion euro dividend to all Stellantis shareholders after the closing.

** FCA's robot unit Comau, initially set to be spun off before the merger with PSA, will now be separated promptly after the closing of the tie-up deal, for the benefit of all shareholders of the combined company.

** China's Dongfeng Motor would reduce its 12.2% stake in PSA by selling 30.7 million shares to the French firm in a move that eased approval for the deal in the United States. Dongfeng to hold 4.5% of the merged group.

** Major shareholders Exor, French state bank Bpifrance Participations and the Peugeot family would be subject to a three-year lock-up period. In that time, the Peugeot family would be allowed to increase its shareholding by up to 2.5% only by acquiring shares from Bpifrance Participations and Dongfeng.

** Exor, the holding company of the Agnelli family which controls FCA with a 28.5% stake, would become the new automaker's single largest investor, with a 14.4% stake.

** A seven-year standstill period following completion of the merger - when extraordinary operations affecting governance cannot be carried out - would apply to Exor, Bpifrance Participations, Dongfeng and the Peugeot family.

** A loyalty scheme for long-term investors will allow Stellantis top shareholders to tighten their grip and head off any potential hostile bidders.

** FCA is being advised by Goldman Sachs and its independent board members by D'Angelin. PSA is being advised by Mediobanca's Messier Maris & Associes and Morgan Stanley, with Perella working for its independent board member. Lazard is advising Exor.

($1 = 0.8135 euros)

(Reporting by Giulio Piovaccari; Editing by Alexander Smith)