<p>Plant–microbial interactions represent a complex biological process in which reactive oxygen species (ROS) play central roles in both plant immunity and symbiosis establishment. ROS act as defense signaling molecules to activate immune responses and as symbiotic cues to regulate microbial colonization. To cope with plant-derived ROS, microbes have evolved sophisticated sensing and scavenging mechanisms; however, a systematic understanding of these responses remains limited. Recent advances in molecular biology and genetics have revealed that microbes can directly sense ROS via transcription factors or indirectly perceive oxidative stress through bio macromolecular damage. They maintain intracellular redox homeostasis through enzymatic antioxidant systems—including catalase (CAT), superoxide dismutase (SOD), and peroxiredoxin/thioredoxin (Prx/Trx)—as well as non-enzymatic mechanisms such as melanin and extracellular polysaccharides. This review systematically summarizes microbial ROS perception and scavenging strategies, highlighting functional distinctions and evolutionary adaptations in pathogenic infection versus symbiosis. These insights provide a theoretical framework for understanding plant–microbial interactions and suggest potential ROS-related strategies for improving agricultural productivity and ecological resilience.</p>