垂簾聽政

Etymology
The idiom arose from a practice in ancient China, by which a royal lady, as an empress or empress dowager, was allowed to preside over the imperial court without actually being seen by her subjects, because women were prohibited from politics. This would usually be done by the mother of a child emperor.

Idiom

 * 1)  (of female royal members, e.g. empress or empress dowager) to rule in place of a monarch; to serve as regent