The China Girls Mathematical Olympiad (CGMO) is a math competition with a proof-based format similar to the International Mathematical Olympiad. It was originally organized in 2002 for teams of girls representing different regions within China. Later, the Chinese organizers decided to invite other nations to send teams of girls from their countries. Russia has participated at least since 2004. The United States first participated in 2007.
References
China Girls Mathematical Olympiad Wikipedia(Text) CC BY-SA