Spencer, who won both an Oscar and a Golden Globe for her 2011 performance in The Help, will play Amity leader Johanna -- a character who features prominently in both the second and third books of Veronica Roth's best-selling trilogy.
Production on Insurgent is expected to begin sometime this month, with theatrical release set for March 2015. Divergent stars Shailene Woodley, Theo James, and Kate Winslet are all expected to reprise their roles in the new movie.
Meanwhile, the third and final book in the series, Allegiant, will actually be split into two films -- a controversial move that many fans think is unnecessary, and greedy on the studio's part.
Earlier today, Lionsgate executives finally spoke out about the decision to split Allegiant, saying they believe there is "more than enough material there to make two substantial, satisfying films."