Loki Ringtones and sound effects. Loki is a fictional character portrayed by Tom Hiddleston in the Marvel Cinematic Universe (MCU). He is based on the Marvel Comics character of the same name. Loki first appeared in Thor (2011) and has since become an important recurring figure of the MCU. As of 2021, the character has appeared in six films, takes the lead role in the live-action series Loki (2021), and a number of alternate timeline variants.