This work gives an overview of all types of constant torque mechanisms (CTMs) based on both function and structure. Based on their architecture, they can be divided into five distinct categories, which all have their specific behavior. It is also shown that these CTMs can be divided into two application types, namely, power assistance or torque stabilization. Constant force mechanisms (CFMs) are more prevalent in the literature; therefore, some discussion is proposed on how CFMs can be transformed into CTMs. It is also shown that some of these CTMs have a very high specific energy, which makes them potentially interesting for use as energy storage/power providers in novel fields like robotics.