Mark Hamill has been recruited by Ukrainian president Volodymyr Zelensky to help fundraise for his country's military efforts in the ongoing conflict with Russia.
The Star Wars actor said he was "honoured" to take on the role of ambassador for the United24 platform.
His role will include raising funds to support Ukrainian defenders, the Drone Army, a project set up by the Ukrainian government to procure unmanned drones to assist the war effort.
The Army of Drones will be used to monitor the 2,470km frontline and provide an effective response to enemy attacks, the project's website said.
Sharing a picture of himself in a virtual meeting with Mr Zelensky, Hamill wrote: "Honoured to be an ambassador for the Army of Drones and to help President Zelensky and the people of Ukraine in any way possible."
The president's official Instagram page also shared the news, writing: "American actor who played Luke Skywalker in Star Wars, Mark Hamill became the ambassador of the UNITED24 fundraising platform.
"He is the first ambassador to help raise funds to support our defenders, the Drone Army.
"This is a difficult yet very important mission. Mark, we are sure you will definitely handle it.
"Thank you for supporting the Ukrainian people in our struggle for freedom," the post added.
It comes following news that Russia will formally annex occupied parts of Ukraine, where it claims that residents had voted to live under Moscow's rule, on Friday.
The Ukrainian government and the West have denounced the Kremlin-organised ballots as illegal, forced and rigged.