Slendytubbies, also known as Slendytubbies 1(acronymed to S1, S, ST or ST1) is an online horror game, which is a result of the combination of popular horror game Slender: The Eight Pages and the children's television show Teletubbies. The game features two modes; Singleplayer and Multiplayer. The Mediafire link of the V2 Beta can be found here, and the original version can be found here. The point of the game is to collect ten bowls of Tubby Custardwhile avoiding Tinky Winky who is the threat of the map.

To this day, Slendytubbies is the most unique installment out of the series: having a interactable environment, three time periods (Dusk wouldn't be reintroduced until a update in Slendytubbies III), different enemy behavior, and more. Interactable environments (such as falling trees) were removed in future installments.