The Titans are the central antagonists of the anime/manga series, Shingeki no Kyojin, known in the western world as, Attack on Titan. Within the Attack on Titan universe, these human-esque monstrosities had nearly brought forth the extinction of the entire human race, with most of the world having been lost and forcing the remaining human beings to retreat inside the confined walls of a massive city state.
Much like the Romero Zombies of modern day horror fiction, Titans are hinted to be an off-shot of the human race now cursed to forever devour the rest of humanity. This was due recent chapters of the series reveals that their nature are almost same with Titan Shifters albeit their human bodies within their titan's nape are crushed and partially assimilated.