The video site, owned by Google, has launched nine versions across Brazil, France, Ireland, Italy, Japan, the Netherlands, Poland, Spain and the UK.
Each site is translated into local languages and has country-specific video rankings and comments.
"Video is universal and allows people around the world to communicate and exchange ideas," said Chad Hurley, YouTube co-founder.
"Our mission is to entertain, inform and empower the world through video."
More than half of all viewers on YouTube were now from outside the US, Mr Hurley added.
YouTube has also unveiled content partners around the world, including deals with France 24, Antena 3 in Spain, European football clubs such as AC Milan, Chelsea, Barcelona and Real Madrid, as well as organisations such as Friends of the Earth and Greenpeace.
"We want to create a YouTube experience that is a local experience," said Steve Chen, the service's other co-founder.
"It's not just about translating, it also about creating content unique to certain countries."