美若天仙

美若天仙 is a stock four-character compliment used almost exclusively for women. The structure is 美 (beautiful) + 若 (like) + 天仙 (heavenly immortal). Common in romance novels, period dramas, and wedding speeches; using it in everyday conversation can sound deliberately flowery or tongue-in-cheek.

culture

天仙 refers to female immortals of Daoist mythology — 嫦娥 (Chang'e, the moon goddess) being the archetype. Comparing a woman to one is the Chinese equivalent of "goddess-like" in English.