What is the main conflict of The Hunger Games?

The main conflict is man vs. man, also known as Katniss against the rest of the 23 tributes. She fights against most of them in the Hunger Games for her life, and that's the main conflict.

Also a bit of man vs. self, as in Katniss fighting with who she is willing to kill and whom she doesn't want to kill. Man vs. nature in the way that the environment of the games is especially perilous.