What Every Woman Knows is a 1921 American silent comedy-drama film adapted form the play What Every Woman Knows by James Barrie. The play had premiered on Broadway in 1908 and was a hit starring Maude Adams. A British silent film version had been made in 1917 and a later American talkie would be produced in 1934 with Helen Hayes. This silent film version was directed by William C. deMille continuing his forte at adapting literary and/or stage plays to the silent screen. The film stars Lois Wilson and Conrad Nagel. This version is now lost.