Ritchie was at London's Dark Knight Rises red carpet premiere on Wednesday (July 18) with Ainsley, who appeared to have a baby bump.
A spokesman for Ritchie told Reveal: "Guy Ritchie and Jacqui Ainsley are thrilled to confirm they are expecting their second child together later this year."
Ainsley gave birth to Ritchie's son Rafael in September 2011, less than two years after they started dating.
Ritchie also has two children with his ex-wife Madonna.
In June, Ritchie signed on to direct the film adaptation of Robert Louis Stevenson's classic novel Treasure Island.