30, is an opéra comique in one act and five scenes by composer Camille Saint-Saëns to a French libretto by Louis Gallet.

[1] The music is characterised by a "light and brisk" quality that uses pentatonic harmony to evoke an "oriental" sound.

La princesse jaune was commissioned for the Opéra-Comique by the company's director, Camille du Locle, as compensation for not being able to mount Saint-Saëns's other opera, Le timbre d’argent, as promised due to financial reasons.

She finds a poem that confirms her suspicion that he is in love with the Japanese woman painted on the panel hung in the cabinet.

An argument erupts when Léna seizes a small bottle that Kornélis brought back with him that morning, and of which he refuses to reveal the contents.

Kornélis resumes pursuing his love affair with Japan, particularly fixating on his portrait of Ming, after the departure of Léna.

She realises that he is in a deluded state and rejects his advances before fleeing the room in fear of more erratic behaviour.

He awakes and she angrily reproaches him for his wild behaviour and his madness for loving a dream, a woman who only exists in his imagination.