Monika "Jac" Jagaciak (Polish: ; born 15 January 1994) is a Polish model. Since signing with IMG Models in 2007 Jagaciak has been given the nickname "Jac" by the agency.
Jagaciak's modeling career began in 2007 after she was encouraged by her sister to attend an open casting of GAGA Models Agency at a shopping center in Poland. She was then picked up by IMG who signed her and in July 2007 she appeared on the cover of French Jalouse. Her big break came at age 13, when Jagaciak went on to land a Hermes campaign for the Fall/Winter 2007 season alongside Daria Werbowy, beating out 600 other candidates while still in primary school. Jagaciak stated in a later interview that before doing the campaign she had never heard of Hermes, nor had she heard of the photographer of the shoot Peter Lindbergh, "I think not knowing helped me stay relaxed" she said. Though Jagaciak's photos incensed some critics, who were upset at the idea of sexualizing girls at such a young age. Soon after, Jagaciak began traveling overseas for her career and in 2008 she traveled to Japan where she landed the cover of Elle. In May 2008, she appeared for the second time on the cover of French Jalouse, and in October 2008 Jagaciak also landed covers for Japanese Harper's Bazaar, and Japanese Spur. Jagaciak was set to appear on the cover of Australian Vogue when the editor decided she was wasn't old enough, and she had to sit out fashion shows due to age regulations.