Victoria Roshchyna, who would have turned 28 this month, disappeared in August last year after travelling to Russian-held east Ukraine for a report.
She remained missing until April 2024, when her father received a letter from Moscow's defense ministry saying she was being held in Russian detention, according to Ukraine's main journalist union.
The circumstances of her arrest were not made public and it was not clear where she was being held inside Russia.
"Unfortunately, information about Victoria's death has been confirmed," said Petro Yatsenko, a spokesperson for Ukraine's prison of war coordination headquarters on Thursday.