"Miyazaki decided to retract his retirement and to make a feature-length animation film," production company Studio Ghibli said on its website.
The studio said that the director, now 76, "found a subject worth turning into" a movie, but added: "This will truly be his final film considering his age."
Miyazaki's most famous works internationally have been "Princess Mononoke" and "Spirited Away", which helped him make the transition from an already widely acclaimed career in Japan to a far broader audience.
"Spirited Away" won the Oscar for best animated feature in 2003, the first Japanese film to do so, and also scooped the Golden Bear prize at the Berlin International Film Festival, among other major gongs.
He began his career in 1963 and his first feature-length film was "The Castle of Cagliostro" in 1979.
He gained critical acclaim and a cult following for "Nausicaa of the Valley of the Wind" in 1984 and co-founded Studio Ghibli, which has become Japan's premier animation studio.