Miki Oyama (大山 美紀, Ōyama Miki) is a one of the hunters chosen by Gantz who participates in the Dinosaur Alien Mission.
Miki was the first to recognize Reika Shimohira while in the room. She didn't contribute at all to the mission or any of the fights, though she did try unsuccessfully to save her friend from the raptors. Despite that she survived the entire dinosaur mission and praised Kei Kurono for his skills, she is shot and killed not soon afterwards by Hikawa and the other vampires.
- The name Miki means "beautiful" (美) (mi) and "chronicle" (紀) (ki).
- Miki's surname Oyama means "big, great" (大) (o) and "mountain, hill" (山) (yama).