Rinat Akhmetov -- the billionaire owner of the Ukrainian soccer club Shakhtar Donetsk -- is taking a third of Mykhailo Mudryk's $75.8 million transfer fee from Chelsea and giving it back to his country ... donating $25 million to help soldiers fighting against Russia.
The 22-year-old winger's move to Chelsea was announced on Sunday ... in a record deal for any Ukrainian team.
Akhmetov -- who's reportedly worth around $4.3 billion -- addressed the transaction on Monday ... saying it's a bittersweet moment for him.
"On the one hand, I am happy for Mykhaylo and proud of him," Akhmetov said in a statement.