Suzanne Collins explained in an interview with School Library Journal that she was inspired to write "The Hunger Games" while channel surfing between reality TV and actual war coverage, both featuring young people. She was really tired, and as the two programs began to blur together, Katniss's story came to her.
Suzanne Collins further explained that her idea for "The Hunger Games" evolved from the Greek myth of Theseus and the Minotaur. In the myth, as punishment for challenging Crete, Athens was forced to send seven boys and seven girls to Crete every 9 years. The children were thrown into the Labyrinth and devoured by the Minotaur, a half-man, half-bull monster.
Finally, the hero, Theseus, volunteered to go, and he slew the monster, ending the atrocities. Basically, Katniss is a futuristic Theseus, but instead of a labyrinth, Collins devised an updated version of the Roman gladiator games.