Designing resilient actuators is a challenge for industry, in part because an index for resilience has yet to be established. In this work, several definitions of resilience are analysed and, on the basis of this, an index quantifying resilience for actuators is proposed. This index does indeed allow for the resilience computation of a wide range of manufactured and biological actuators to be compared. The two manufactured actuators chosen as iconic models are a hydraulic cylinder and a bio-inspired McKibben muscle, and these are shown not to be resilient by design. In addition, two biological actuators likely to be resilient were also analysed. The pulvinus resilience index shows that it is partly resilient depending on damage location. But the most promising is the skeletal muscle, which has been shown to be highly resilient. Finally, the bio-inspired roots of resilience are discussed: resilience may originate from multi-scale structural design.