Zebrafish (Danio rerio) Interleukin-8 (IL-8), commonly referred to as Cxcl8 (with duplicated paralogs such as cxcl8a and cxcl8b in teleosts), is a key pro-inflammatory chemokine that regulates neutrophil recruitment and activation during innate immune responses. Functionally analogous to mammalian IL-8, zebrafish IL-8 is rapidly induced in response to bacterial infections (e.g., Mycobacterium marinum, Streptococcus spp.), viral challenges, tissue injury, and inflammatory stimuli, and signals through CXCR1- and CXCR2-like receptors to promote directed neutrophil migration to sites of infection or damage. Due to the optical transparency of zebrafish larvae and availability of fluorescent neutrophil reporter lines, IL-8–mediated chemotaxis can be visualized in real time, making zebrafish a powerful in vivo model for studying leukocyte trafficking, wound healing, granuloma formation, and tumor-associated inflammation. Dysregulated IL-8/CXCR signaling has been implicated in chronic inflammation and cancer progression in zebrafish models. As both a biomarker and functional mediator of neutrophil-driven inflammation, zebrafish IL-8 supports high-throughput drug screening, genetic manipulation studies, and comparative immunology research, reinforcing its value as a versatile vertebrate model for investigating chemokine biology and inflammatory disease mechanisms.