The 19-year-old actress was joined at the annual bash by Girls star Allison Williams, who showed off her brand new engagement ring.
Earlier in the week, Saoirse was spotted carrying a large pink bag in her hands while arriving at LAX Airport in Los Angeles.
FYI: Saoirse is wearing a Valentino gown, Brian Atwood shoes, Rona Pfeiffer earrings, and a Graziela ring. Allison is wearing an Emilia Wickstead dress, Brian Atwood shoes, Van Cleef & Arpels jewelry, and a Roger Vivier bag.
10+ pics inside of Saoirse Ronan and Allison Williams at the Vanity Fair party…