In this study, we present a distinctive phenomenon of strain localization observed in pre-strained AZ31 alloy during tensile deformation. The strain localization behavior involves the repetitive formation, propagation, and subsequent annihilation of localized deformation bands within the gage section of the specimen. Although this strain localization behavior bears resemblance to the Portevin–Le Chatelier (PLC) effect commonly observed in steels and Al-Mg alloys, it is driven by a fundamentally different mechanism. Through detailed microstructural analysis, we reveal that this unique strain localization is closely associated with the process of de-twinning. Our findings contribute to a deeper understanding of the deformation behavior in magnesium alloys and offer new insights for the strain localization in metals. Display omitted