Pope Francis has written a letter to the Ukrainian people that was published on Friday by the Vatican.
"Not a day goes by that I am not close to you and hold you in my heart and prayers," the Pope said in the letter, which was originally written in Italian.
"Your pain is my pain," he wrote.
Francis did not mention Russia, but asked: "How is it possible that men can treat other men this way?"
The Pope mentioned the suffering of young Ukrainian children killed and displaced people who have had to flee the war.
"In each one of them is the defeat of the whole of humanity," he said.
The letter expressed sympathy for young people "who have had to take up weapons to courageously defend their country," mothers who have lost husbands, the elderly and volunteers.
"In this ocean of evil and pain," the Pope wrote, "ninety years from the terrible Holodomor genocide, I admire your ardor. Even in the immense tragedy you are suffering, the Ukrainian people has never become discouraged or abandoned themselves to commiseration."
The 1932-1933 Holodomor, or Terror Famine, was artificially engineered by the Soviet leader Joseph Stalin, who removed food stocks from Ukrainian peasants, leading to the deaths of millions of people.
"The world has recognized a bold and strong people, a people who suffer and pray, weep and fight, resist and hope, a noble and martyred people," the Pope added.