Abstract: Seeds of Euphorbia lathyris L. accumulate a substantial amount of oil enriched with oleic acid. The plant transcription factor WRINKLED1 (WRI1) is a member of the AP2/EREBP transcription factor family, which is involved in the regulation of fatty acid synthesis and seed development. Based on the whole genome data of E. lathyris, 11 ElWRI1 genes were identified, namely ElWRI1-1–ElWRI1-11, respectively. All identified ElWRI1s contained two AP2 domains. The ElWRI1 proteins were unstable hydrophilic proteins, lacking a transmembrane structure. The 11 ElWRI1 proteins were predicted to localize in the nucleus. Heatmap analysis revealed that ElWRI1-6 and ElWRI1-8 exhibited higher expression levels, with the expression pattern of ElWRI1-8 mirroring that of seed oil accumulation. Heterologous overexpression of ElWRI1-8 in Nicotiana benthamiana L. leaf tissues led to a significant increase in total oil and oleic acid contents in the leaf. This study indicates that ElWRI1-8 is an important transcription factor in regulating biosynthesis of oil and oleic acid in E. lathyris seeds, thus providing a new scientific basis for the high-yield and high-quality breeding of E. lathyris and the development of high-value oil products.