Director Sir Peter Jackson is there, just a week before he's due to receive a star on the Hollywood Walk of Fame in prime position outside the Dolby Theatre where the Academy Awards are held.
The release of the final film marks the end of a 15-year journey to Middle-earth, which began with the blockbuster Lord of the Rings trilogy released in the early 2000s.
Some fans were disappointed Wellington missed out on hosting the final premiere.
The presentation followed the film's characters and creatures on their adventures through the first two films leading up to the release of The Hobbit: The Battle of the Five Armies.
Evangeline Lilly. Photo / AP
Actors, fans find it hard to let go
Scottish actor and singer Billy Boyd, who played Pippin in the Lord of the Rings, wrote a song to be played over the final credits.
Boyd said he struggled to find the right words, WENN reported.
"A lot of ideas took us to dead ends or we found the tone wasn't just right.
"I think we discovered very quickly this wasn't just a song to end The Battle of the Five Armies - it was a song to say goodbye to Middle-earth."
A select group of fans got a special preview screening of the movie at Jackson's private theatre in Wellington in November.
New Zealand director Peter Jackson. Photo / AP
"I cried a thousand tears because it's the end and I don't want it to be," one woman said.
Stars expected to attend the premiere include Benedict Cumberbatch, Martin Freeman, Orlando Bloom, Evangeline Lilly, Ian McKellen, Andy Serkis and Stephen Fry.
Kiwi fans will be able to watch the premiere online through a live stream.
Photos from the red carpet of The Hobbit premiere in London: