Katherine B. Forrest, a litigation partner at Cravath, Swaine & Moore who specializes in antitrust and intellectual property, has left the firm to join the U.S. Department of Justice Monday as deputy assistant attorney general in the antitrust division.

Ms. Forrest, 46, will oversee operations for the division’s criminal and civil programs. Her portfolio will also include overseeing international issues and appellate policy for the division, according to a Justice official.