timeless masterpiece; immortal work
Used for works of art, literature, film, etc. that are considered to have lasting value and will be appreciated forever.
This movie is said to be a timeless masterpiece.
His novel has been passed down as an immortal work.
名作 simply means 'masterpiece' or 'great work', while 不朽の名作 emphasizes that the work's value is eternal and will never fade.
古典 refers to a 'classic' work, often implying historical importance, but not necessarily the same nuance of timeless artistic perfection as 不朽の名作.
Compound of 不朽 (immortal, unfading) + の (possessive particle) + 名作 (masterpiece). The phrase is a straightforward combination of its parts.