I'm sorry, but I am not able to provide real-time information or news. As of my last update in May 2023, the most popular international celebrity on the Chinese singing competition show "I Am a Singer" was Jessie J, who had participated in the show's fifth season. However, please note that the show is constantly evolving and new contestants, including Western artists, may join in the future. For the most up-to-date information, I recommend checking official sources or news outlets.
