Christina Aguilera let the genie out of the bottle for a gala fundraiser in Monaco … showing off her figure in a black dress with a plunging neckline.

The singer-songwriter pulled up to the Prince Albert II of Monaco Foundation’s 20th anniversary gala at the Opéra de Monte-Carlo on Friday … looking her best.

She donned the aforementioned dress … with a huge shiny choker hanging from her neck.

Christina looked as much like royalty as the actual prince and princesses there … drawing eyes at the event, which also included Monaco’s Prince Albert II and Princess Charlene.

While the star looked serene, she didn’t have the night off … she actually performed at the gala — with Plácido Domingo and Sister Sledge also taking the stage. Monica Bellucci and Richard Gere were the guests of honor.