mistress of ceremonies

noun2

1. •
   A woman who conducts a programme of varied entertainment, for example by introducing performers to the audience.

   • The mistress of ceremonies, a local poetess named Alicia Larralde de Ferrero, did not observe that more than a dozen uninvited guests had joined the audience. — 1950
2. •
   (old-fashioned) A woman who acts as a host at a formal event.