Sean Penn is currently in the thick of Russia's invasion on Ukraine as he is filming a documentary.
The actor and director, 61, appeared in the country's capital, Kyiv, on Thursday as Putin declared war on Ukraine.
Sean's documentary will "tell the world the truth about what's going down," according to Ukrainians.
He turned up at a meeting today in Kyiv, with Ukraine's Government saying he is there to capture the conflict on film.
The Office of the President of Ukraine says Sean is showing "courage and honesty".
Sean was sat in the audience of a press briefing, listening to Government officials.
It's reported he also spoke to journalists and the military in a bid to understand how the Ukrainians are mounting a defence, according to TMZ.
According to the publication, Sean first arrived in the country back in November, in preparation for his documentary.
The documentary is a VICE Studios production, 'in association with VICE World News and Endeavor Content,' according to a spokesman for the media company.
In a Facebook post today, the Ukrainian government said it was grateful for Sean being there.
The post said: "An American actor and filmmaker, Oscar winner Sean Penn arrived to Ukraine. The director specially came to Kyiv to record all the events that are currently happening in Ukraine and to tell the world the truth about Russia's invasion of our country.
"Sean Penn is among those who support Ukraine in Ukraine today. Our country is grateful to him for such a show of courage and honesty."
The statement concluded: "The more such people, true friends of Ukraine, who support the fight for freedom, the sooner it will be possible to stop the massive attack on Russia."
Penn is settling in while thousands of others try desperately to flee the country.
The attack in Ukraine, described by Boris Johnson as a "vast invasion", began early on Thursday with a series of precision missile strikes and air strikes followed by ground troops crossing the border.
The first targets included Ukrainian air defences, designed to ensure Russia's aerial superiority in the conflict.
So far, officials say that it is unclear whether he intends to take control of the entire country.
However they believe that his objectives include the capital Kyiv and the port city of Odesa as well as joining up Crimea, which he seized in 2014, with the Donbas.
Officials believe that Russian special forces are now active inside Ukraine conducting operations to soften resistance in ahead of the main conventional forces advance.
There are particular concerns now about the prospect of an assault on Kyiv, a city with a population of more than 2.8 million.
In the past, such as in the Chechen capital Grozny, Russian forces having shown they are willing to use overwhelming firepower if they cannot achieve their objectives quickly, potentially resulting in large-scale civilian casualties.
