Epigenetic pathways could provide a mechanistic explanation for inheritance of acquired characteristics, as proposed by Lamarck in 1802, but epigenetic alterations that endow adaptive hereditary traits have rarely been observed. Here, in cultivated Asian rice (Oryza Sativa L.), we identified an epiallele conferring acquired and heritable cold tolerance, an adaptive trait enabling northward spread from its tropical origins. We subjected cold-sensitive rice to multigenerational cold stress and identified a line with acquired stable inheritance of cold tolerance. DNA hypomethylation variation in the Acquired Cold Tolerance 1 (ACT1) promoter region rendered its expression insensitive to cold. This change is in large part responsible for the acquired cold tolerance, as confirmed by DNA-methylation editing. Natural variation in ACT1 DNA hypomethylation is associated with cold tolerance and rice geographic distribution. Hypomethylation at ACT1 triggers adaptive cold tolerance, presenting a route to epigenetic-variation-driven inheritance of acquired characteristics.