The car company behind the brands Vauxhall, Jeep and Fiat says US President Donald Trump's tariffs have already cost it €300m (£259.6m, $349.2m).
Stellantis said the financial hit was a result of tariffs impacting trade and the company's loss of planned production in its response to the them.
A 25% tariff on cars being imported to the US has been place since April.
Trump's policy decision has threatened to upend global car trade and supply chains, with some car manufacturers, including Jaguar Land Rover (JLR) temporarily pausing exports to the US in response.
Stellantis owns 14 car brands, including Alfa Romeo, Maserati, Citroen, Chrysler and Dodge.
It said its shipments to North America were 25% lower in the three months to June compared to the same period in 2024, due in part to tariffs.
Total sales over that time were also down 10%, the company said in preliminary figures for the first half of the year.
While Stellantis has manufacturing plants in the US, it also manufactures vehicles in the UK, Europe, Canada, Mexico and South America.
The car company has forecast revenues of €74.3bn for the first half of the year, and a net loss of €2.3bn which includes the impact of tariffs.
When he introduced the car tariffs, Trump said it would boost the American car manufacturing industry, but within a month of their introduction he eased tariffs on foreign car parts.
The UK reached a deal with the White House in May to reduce car tariffs to 10% on up to 100,000 vehicles, which is still considerably higher than the previous tariff of 2.5%.
Other countries remain in negotiations with the US, and Trump has recently threatened to lift overall tariffs on the European Union and Mexico if they retaliate against the US tariff regime.
Trump has also threatened to lift tariffs on Brazilian exports to 50% if the country does not drop a case against far-right former president Jair Bosonaro, a Trump ally facing prosecution over an alleged coup plot.
Stellantis has three facilities in Brazil, producing Fiat, Jeep and Citroen vehicles.
Stellantis is not the only car manufacturer dealing with the repercussions of Trump's tariffs.
In June, JLR downgraded its profit predictions after it halted all exports to the US in April before resuming shipments in May after the UK deal was reached.
Last week, JLR announced it was cutting up to 500 management jobs in the UK amid ongoing pressure on its sales from tariffs.