Knightley and Adam Levine have been filming their new movie Can a Song Save Your Life? in New York. The pair play a couple who move to the city with the hope of securing record deals. The film also stars Mark Ruffalo, whose character discovers Greta (Knightley) singing in a bar on an open mic night.
In the Czech Republic, Helen Mirren received a Lifetime Achievement Award at the 47th Karlovy Vary International film festival. She arrived at the event with husband Taylor Hackford and was presented with flowers by the organisers.
Meanwhile in Sydney, Katy Perry walked the pink carpet as she arrived for the premiere of Part of Me. The film documents her life on and off stage, and features interviews with the star as she embarks on her tour and divorce from Russell Brand.
Scroll through our gallery below to see today's celebrity pictures.