“Que sera, sera” isn’t actually correct in any real language; it’s a made‑up, pseudo–Romance phrase that mixes Spanish/Italian-looking words on English grammar.

More detail:

  • The words look Spanish or Italian (“que/qué” and “será/serà”), but the structure is ungrammatical in both languages.
  • In Spanish, a grammatically natural version would be closer to “lo que será, será.”
  • In Italian, it would be more like “che sarà, sarà.”
  • The catchy phrase was popularized in English by the 1956 Doris Day song “Que Sera, Sera (Whatever Will Be, Will Be),” so in practice most people treat it as an English idiom meaning “whatever will be, will be.”

So if you have to pick one, you’d usually call it an English expression built from faux Spanish/Italian, not a genuine Spanish or Italian sentence.