Gwen Stefani and Jessica Alba were among the A-listers to attend the party Richie and husband Joel Madden threw to mark Harlow's special day.
The 29-year-old reality TV star hosted the party at the Tree House Social Club in Beverly Hills.
Gwen and husband Gavin Rossdale brought their sons Kingston and Zuma along, while Jessica and her partner Cash Warren took their daughter Honor.
Grey's Anatomy star Ellen Pompeo and her child Stella, as well as Kourtney Kardashian and her son Mason, were just some of the other guests who turned up on the day.