Best described as films primarily interested in their characters' unhinged state of mind, psychological thrillers are more concerned with showing altered, imbalanced emotional states than they are outright violence, though many contain striking uses of it. A close relative of the horror film (many regard serial killers) and the paranoid-conspiracy thriller (examples of which can be found within), the psychological thriller is a far broader genre than most, often creeping its way into everything from drama to sci-fi. It's no surprise that many of the films contained within this list are not only some of the greatest psychological thrillers of all time, but some of the greatest films of all time, period - such is this genre's reach. At least ten of the films presented here are certified, Greatest Of All Time classics, while the other ten fall someplace between Hidden Gem and Something in Between. What's certain about all of them is that they are essential to the genre, psychological thrillers in the very best vein, looking to twist and turn and invert your brain matter until it resembles that of whoever is unfortunate enough to be on screen at the time.