Lignin is not only important for plant growth and development but is also a major player in the response of plants to various biotic and abiotic stresses. Although the link between lignin and stresses has been widely demonstrated, the chemical nature and especially the molecular mechanisms underlying the biosynthesis of stress lignin remain largely unknown. Recent findings suggest that the structure of the polymer produced de novo seems to largely depend on the type and intensity of the stress and on the plant species. In addition, the control of stress-related lignification might also occur at several regulatory levels, including transcriptional, posttranscriptional, and posttranslational, similar to developmental lignification. This review focuses on the recent advances on the function, structure, and regulation of lignin deposited upon stress.