<p>Fun activities are intrinsically rewarding, evoking positive feelings and memories. However, some activities are not obviously fun, such as an arduous backpacking trip. Outdoor educators call this “Type 2” fun (Strout, 2022). Theoretically, Type 2 fun can be a critical ingredient in outdoor education (Deane &amp; Harré, 2013); however, a search of the peer-reviewed literature found no descriptions of Type 2 fun. To bring this concept into the realm of scientific investigation, this theoretical paper uses theories of stress and well-being to define four types of fun. The four types of fun (4TF) model combines professional wisdom and psychoeducational theory, refines and extends the types of fun described in colloquial outdoor literature, and provides a theoretical framework that describes four types of fun and four types of experiences that are not fun. This model is important because different types of fun could distinguish between experiences that stimulate positive development and those with neutral or negative effects in the context of outdoor education.</p>