LAUSR

π‐Conjugated polymers have drawn broad interest in flexible electronics due to their solution processability, light weight, and a combination of conducting and light‐emitting properties. However, achieving mechanical endurance and stretchability in freestanding conjugated polymers is still difficult. Surface‐assembly‐induced light‐emitting polymer nanosheets with prodigious mechanical strength and charge transport are reported. Transferring freestanding polymer films onto various templates with conformal contact results in electrical and optical strain sensors with a gauge factor of ≈29. Subsequent geometric engineering into kirigami structures of the polymer sheets further extends the strain accommodations 20‐fold without compromising electric conductivity or fluorescence properties. These as‐prepared semiconducting polymers represent a possible new material for emerging stretchable electronics.