Rory Mason’s father Rob has paid tribute to his son describing him as a “young man of drive, purpose and conviction.”
Rory Mason, 23, died as a Ukrainian armed forces serviceman while fighting in the International Legion for the Defence of Ukraine near the Russian border.
The Mason family learnt of Rory's death from the Department of Foreign Affairs, which is providing consular assistance.
His father Rob said: "Rory was a private young man of drive, purpose and conviction.
"Though we are deeply saddened at his death, we are enormously proud of his courage and determination and his selflessness in immediately enlisting to support Ukraine.
"Rory was never political but he had a deep sense of right and wrong and an inability to turn the other way in the face of injustice.
"He had a long-standing interest in eastern Europe, in travel and in learning new languages, including Russian. Those who fought alongside Rory speak of 'a truly brave and courageous man who could have left at any time but chose not to'.
"Rory was our son and we will miss him enormously. As our family is still trying to come to terms with Rory's death, we would appeal for privacy at this difficult time".
The International Legion For The Defence Of Ukraine said Rory Mason's memory will live on.
"Our brother in arms, Rory Mason has taken part in the Kharkiv counteroffensive with his unit and was killed in action," a spokesman said in a statement.
"While conducting operations, the unit came under attack.
"We are in contact with the family and in co-ordination with them, following their wishes and instructions, the International Legion and the armed forces of Ukraine are handling the repatriation process.
"At this time, to protect operational security and the family's privacy we cannot release more information.
"Rory's memory will live on in his unit, in the legion and the armed forces of Ukraine.
"We would ask for the family's privacy to be respected at this difficult time."