<p>Aquaculture practices have evolved significantly from low-density to highly intensive systems, increasing susceptibility to disease outbreaks. Conventional disease prevention relying on antimicrobials and chemotherapeutics causes detrimental environmental impacts and contributes to antimicrobial resistance (AMR). Consequently, the use of vaccines and immunostimulants offers promising environmentally sustainable alternatives. In fish, unlike in higher vertebrate, innate immunity, mediated by pattern recognition receptors (PRRs), plays a dominant role in defence against diseases. Among PRRs, retinoic acid–inducible gene I (RIG-I)–like receptors (RLRs: RIG-I, MDA5, and LgP2) are critical viral sensors triggering the synthesis of type I interferon production and antiviral responses. Over the years, rapid identification of fish RLRs and their downstream signalling molecules is enabling novel infection-prevention strategies. This comprehensive review synthesizes the current and updated research on fish RLRs, addressing their history of identification, spliced variants, polymorphism, ontogenic expression, subcellular localization, architectural insights, signal transduction pathways, response against pathogens and environmental stressors, impact of their modifications on innate immunity, and the regulators that inhibit RLR-signalling pathways. Understanding the functions of fish RLRs is likely to be helpful in advanced vaccine design incorporating multiple RLR ligands as adjuvants resulting in enhanced immunity and disease resistance for the sustainable aquaculture.</p>