In English, long pig is human flesh eaten by cannibals. As I couldn't find a French equivalent for it in any of the dictionaries that I can look up into, I was wondering if anyone knows a good French translation for this imaginative expression.
Long Pig is a culinary term that refers to human beings. The most accurate translation would be "Chair humaine".
You could also use "Bidoche" or "Barbaque" if you want slang words about "Viande" (aka meat).
From wikipedia about Cannibalism:
There is no French equivalent that I could find.
All there is, is the original Marquesaan (Polynesian) word "puaa ao" which can be translated into English as "long pig that speaks". You could translate that literally : "Le grand porc / cochon qui parle".
I have never heard of a similar expression. To convey meaning, my best guess would be to translate it simply by “chair humaine” (literally “human flesh”). If you want to preserve style, I can think of anything better than @Kwaio.