Tim Blake Nelson and Austin Stowell are also on board with Nacho Vigalondo writing and directing.
The story follows a woman who moves back to her hometown after losing her job and boyfriend in New York, only to discover that she is somehow strangely connected to a giant creature that has materialized over Seoul and is wreaking havoc on the city.
Stevens will play the ex-boyfriend who originally scorns her only to later fight to win her back.
The film is currently in production in Vancouver.
Voltage Pictures is handling international sales while CAA is repping domestic rights. “Colossal” marks the first film to go into production under the recently announced five-picture sales deal between Voltage and Brightlight.
Stevens, who used to star in “Downton Abbey,” is coming off a busy 2014 that included “The Guest,” “A Walk Among the Tombstones” and “Night at the Museum: Secret of the Tomb.” He can be seen next in the indie “Criminal Activities,” as well as in the role of the Beast in Disney’s live-action adaptation of “Beauty and the Beast,” also starring Emma Watson.
He is repped by WME, Julian Belfrage Associates and Peikoff Mahan Law Office.