Cameron is preparing to start production on the trio later this year in what will be a highly scrutinised next move, given that Avatar ranks as the biggest ever global release in the pantheon of unadjusted grosses.
Fox will release the films worldwide one year apart, starting in December 2016.
“Sigourney and I have a long creative history, dating back to 1985 when we made Aliens,” said Cameron in a statement.
“We’re good friends who’ve always worked well together, so it just feels right that she’s coming back for the Avatar sequels.
“Her character of Grace Augustine, as fans know, died in the first movie, so she’s playing a different and in many ways more challenging character in the upcoming films. We’re both looking forward to this new creative challenge, the latest chapter in our long and continuing collaboration.”
Avatar opened in December 2009 and went on to gross $2.78bn worldwide, taking $760.5m in North America and a little over $2bn internationally.