magnum opus

US /ˌmæɡ.nəm ˈoʊ.pəs/
UK /ˌmæɡ.nəm ˈoʊ.pəs/
"magnum opus" picture
1.

magnum opus, chef-d'œuvre

a large and important work of art, music, or literature, especially one regarded as the most important work of an artist or writer.

:
His latest novel is considered his magnum opus.
Son dernier roman est considéré comme son magnum opus.
The symphony is widely regarded as the composer's magnum opus.
La symphonie est largement considérée comme le magnum opus du compositeur.