Ciboria shiraiana is a necrotrophic fungus that causes mulberry sclerotinia disease resulting in huge economic losses in agriculture. During infection, fungus utilizes immunity elicitors to induce plant tissue necrosis which could facilitate its colonization on plants. However, the key elicitors and immune mechanisms remain unclear in C. shiraiana. Herein, a novel elicitor Cs08297 secreted by C.shiraiana was identified, and it was found to target the apoplast in plants to induce cell death. Cs08297was a cysteine-rich protein unique to C. shiraiana, and cysteine residues in Cs08297 were crucial for its ability to induce cell death. As observed, Cs08297 induced a series of defense responses in Nicotiana benthamiana,including the burst of reactive oxygen species(ROS),callose deposition,and activation of defense-related genes. Further, Cs08297 induced-cell death was mediated by leucine-rich repeat( LRR) receptor-like kinases BAK1 and SOBIR1. Purified His-tagged Cs08297-thioredoxin fusion protein triggered cell death in different plants and enhanced plant resistance to diseases. Also, Cs08297was necessary for sclerotial development, oxidative-stress adaptation, and cell wall integrity but negatively regulated virulence of C. shiraiana. In conclusion, our results revealed that Cs08297 was a novel elicitor in fungi inducing plant immunity. Furthermore, its potential to enhance plant resistance provided a new target to control agricultural diseases biologically.