US actress Jessica Chastain met Ukrainian President Volodymyr Zelenskyy in Kyiv at the weekend during a trip to the war-torn country that included a visit to a children's hospital.
Her visit comes as the White House and the United Nations have called on Russia to halt military operations near nuclear power plants in Ukraine.
Mr Zelenskyy thanked Chastain for her support in a post on the Telegram messenger app.
“For us, such visits of famous people are extremely valuable,” he wrote.
“Thanks to this, the world will hear, know and understand the truth about what is happening in our country even more.”
Chastain also visited Okhmatdyt Children's Hospital, Ukraine's national news agency reported.
The actress joined the growing list of A-listers who have visited Ukraine in a show of support for the country following Russia's invasion.
Mr Zelenskyy has held meetings with actors Sean Penn and Ben Stiller, and actress Angelina Jolie visited Lviv to meet people displaced by the war.
Earlier this year, Hollywood power couple Mila Kunis and Ashton Kutcher created a GoFundMe, which raised more than $30 million. Kunis was born in Ukraine and moved to the US when she was eight.
Chastain's trip comes after the Ukrainian first lady, Olena Zelenska, pleaded with members of US Congress in late July to send more military aid to her country. Mr Zelenskyy's wife shared stories of women and children killed by Russian forces to make clear the brutality of the war faced by Ukraine.