Speaking at the London premiere of his latest film, A Hologram for the King, on Monday night, Hanks took a jab at the Republican contender's hopes of ever sitting behind a desk in the Oval Office.
"I think that man will be president right about the time when spaceships come down filled with dinosaurs in red capes," Hanks told Sky News on the red carpet.
Hanks, 59, also took aim at Trump's central campaign slogan: "Make America Great Again."
"Here's the problem: America's already great, so I don't know what he is talking about," said the two-time Oscar winner. Hanks, alongside fellow Hollywood heavyweights Steven Spielberg and George Clooney, is an open supporter of Hillary Clinton for President.
RELATED VIDEO: Sally Field Calls Donald Trump 'Overrated'
In August 2015 he joined Kim Kardashian West, Kanye West, Jessica Alba and Usher at a $2,700-per-ticket Clinton fundraiser at the Brentwood home of Justin Bieber's manager, Scooter Braun.
Clooney and wife Amal also hosted their own Clinton fundraiser in L.A. earlier this month. Alongside Jane Fonda, Ellen DeGeneres, Portia de Rossi and Jim Parsons, the guests included competition winners Alisa and Rob Bair from Lancaster County, Pennsylvania, who described the night to PEOPLE as "unforgettable and incredibly special" – not least because they sat with Clinton and the Clooneys during the fundraising meal.
"It was mind-blowing," Alisa Bair told PEOPLE. "I looked up from my meal at George and Amal and Hillary and thought, 'Holy cow, I am sitting across from these people. I'm eating my salad with them.' "