The film, a sequel to the 2018 DC Comics film Aquaman, will see Momoa reprise the role of Arthur Curry, the half-human heir to the throne of Atlantis.
The Game of Thrones star shared a video on Instagram announcing that filming had begun.
“London calling!… so excited to start Aqua-man 2, we are here! goodbye brown hello blondie,” he wrote.
“Mahalo to everyone for support on the HD Momoa line with @harleydavidson and all my love to the cast and crew of SEE ! Love u Canada link in bio! Aloha j.”
In the video, Momoa is seen wearing glasses and discussing altering his hairstyle for the role, which begins filming today (19 July).
At the time of writing, the post has amassed nearly 3 million views.
The Lost Kingdom will be directed by James Wan, who also directed the first Aquaman film.
Co-stars Amber Heard, Patrick Wilson, Dolph Lundgren and Yahya Abdul-Mateen II will also be reprising their roles from Aquaman for the sequel.