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Wearable devices benefit from the use of stretchable conjugated polymers (CPs). Traditionally, the design of stretchable CPs is based on the assumption that a low elastic modulus (E) is crucial for achieving high stretchability. However, this research, which analyzes the mechanical properties of 65 CP thin films, challenges this notion. It is discovered that softness alone does not determine stretchability; rather, it is the degree of entanglement that is critical. This means that rigid CPs can also exhibit high stretchability, contradicting conventional wisdom. To inverstigate further, the mechanical behavior, electrical properties, and deformation mechanism of two model CPs: a glassy poly(3‐butylthiophene‐2,5‐diyl) (P3BT) with an E of 2.2 GPa and a viscoelastic poly(3‐octylthiophene‐2,5‐diyl) (P3OT) with an E of 86 MPa, are studied. Ex situ transmission X‐ray scattering and polarized UV–vis spectroscopy revealed that …