The actor and comedian said that Johnson impressed him when he appeared on David Letterman's chatshow in the US, declaring that he would make a great leader of the UK.
"He would change the face of what a national leader could be. He's charming, very funny – and has that weird hair," he told The Sun.
Galifianakis currently stars as Marty Huggins in The Campaign alongside Will Ferrell, which satirises what politicians will do in order to win votes during an election.
He added that he was envious of the UK's election process in comparison to his own country.
"You guys only campaign for a certain number of days. That's amazing – it's so civil," he said.
"But that will never happen over here because the media love these races that go on for two years. The movie is about how insane stuff has gotten."
The Campaign was released on September 28.
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