Bianca Castafiore (Italian pronunciation: [ˈbjaŋka kastaˈfjoːre]), nicknamed the "Milanese Nightingale" (French: le Rossignol milanais), is a fictional character in The Adventures of Tintin, the comics series by Belgian cartoonist Hergé.

While famous and revered the world over, most of the main characters find her voice shrill and appallingly loud, most notably Captain Haddock, who ironically is the object of Castafiore's affections.

Castafiore is comically portrayed as narcissistic, whimsical, absent-minded, and talkative, but often shows a more generous and essentially amiable side, in addition to an iron will.

She is played on radio in Land of Black Gold and in Tintin in Tibet, Captain Haddock imagines her singing in Flight 714 to Sydney, and mentions her famous aria in Destination Moon.

Although she is apparently one of the leading opera singers of her generation, the only thing that Castafiore is ever heard to sing are a few lines of her signature aria, "The Jewel Song" (l'air des bijoux, from Gounod's Faust), always at ear-splitting volume (and violent force—certainly enough to part the Captain's hair, shatter glasses and a breeze enough to blow back a curtain in an opera box—"She's in fine voice tonight.").

Their ruse backfired, not least because Castafiore expressed her contempt for her show trial and her life sentence with her trademark ear-splitting rendition of the Jewel Song.

Oddly, the lead-in (played by an invisible orchestra) is the introduction to yet another coloratura aria, "Una voce poco fa", from Rossini's Barber of Seville.