Jasmonic acid (JA) is a significant plant hormone that plays a defensive role in plants under stress conditions. The complex production, signaling mechanisms, and regulatory functions of JA are highlighted in this chapter, highlighting its function to mitigate biotic stress, such as disease, pest, and herbivore attacks. A complex network of MYC transcription factors, COI1 receptors, and JAZ proteins indicates the functioning of JA. This network coordinates under conditions of systemic and localized resistance, including induced systemic resistance (ISR). The chapter further emphasizes the ecological and agricultural applications of JA and its derivatives, highlighting their significant role in sustainable crop protection and pest management. Despite its promising prospects, various challenges also arise, such as environmental variability and scalability, which require further investigation. Further research on JA-mediated defense mechanisms illustrates a pathway for the enhancement of global food security and promoting resilient agricultural practices during rising challenges. Additionally, JA interacts with other plant hormones, such as salicylic acid (SA), auxins (IAA), gibberellins (GA), and abscisic acid (ABA), which all work together to fine-tune the balance between plant growth and defense.