인생작 (insaengjak) — A personal all-time favorite work.

Lesson 82 in our Korean Slang series, adapted from Korean Your Teacher Doesn’t Teach You by Injin Hwang. This expression appears in the book’s shortened expressions section.
What 인생작 means
A novel or film can become your 인생작 when it stays meaningful long after you finish it. The 작 here refers to a creative work. The situation and tone help determine how natural the expression sounds.
A short conversation
A: 그 영화를 또 보네?
B: 응, 내 인생작이야.
A: Watching that movie again?
B: Yes, it is my all-time favorite.
Use it with care
It is a personal judgment, not a claim that everyone must rank the work first. You can explain what made it special to you.
A neutral or polite alternative: 제가 가장 좋아하는 작품이에요. — It is my favorite work.
Try it yourself
Can different people have different 인생작?
Answer: Of course. It is subjective. Read the Korean exchange aloud, then replace one detail with something from your own life.
Learn the rest of the series in Basic Korean Grammar. Find more expressions in the Korean slang book on Amazon.