Streptococci are primary colonizers of the oral cavity, playing a dual role in health and disease. They are essential for maintaining oral health by shaping the microbiota, modulating the immune system, and preventing pathogen colonization. However, some species, like *Streptococcus mutans* and *Streptococcus sobrinus*, can cause dental caries. In periodontitis, they facilitate the colonization of late biofilm formers, leading to gingival pocket infections. Streptococcal virulence is enhanced when they disseminate into the bloodstream, causing systemic diseases such as infective endocarditis and hemorrhagic stroke. This review discusses the taxonomic diversity of oral streptococci, their roles in oral health and disease, and their virulence factors. Key virulence factors include adhesins like AgI/II, cell surface glycoproteins like Cnm, rhamnose-glucose polysaccharide (RGP), lipoteichoic acid (LTA), glycosyltransferases, and nuclease proteins. These factors contribute to biofilm formation, immune modulation, and evasion of host defenses. Oral streptococci also produce hydrogen peroxide and secondary metabolites that influence immune responses and bacterial interactions. Understanding these mechanisms is crucial for developing therapeutic interventions and vaccines to prevent oral and systemic diseases.Streptococci are primary colonizers of the oral cavity, playing a dual role in health and disease. They are essential for maintaining oral health by shaping the microbiota, modulating the immune system, and preventing pathogen colonization. However, some species, like *Streptococcus mutans* and *Streptococcus sobrinus*, can cause dental caries. In periodontitis, they facilitate the colonization of late biofilm formers, leading to gingival pocket infections. Streptococcal virulence is enhanced when they disseminate into the bloodstream, causing systemic diseases such as infective endocarditis and hemorrhagic stroke. This review discusses the taxonomic diversity of oral streptococci, their roles in oral health and disease, and their virulence factors. Key virulence factors include adhesins like AgI/II, cell surface glycoproteins like Cnm, rhamnose-glucose polysaccharide (RGP), lipoteichoic acid (LTA), glycosyltransferases, and nuclease proteins. These factors contribute to biofilm formation, immune modulation, and evasion of host defenses. Oral streptococci also produce hydrogen peroxide and secondary metabolites that influence immune responses and bacterial interactions. Understanding these mechanisms is crucial for developing therapeutic interventions and vaccines to prevent oral and systemic diseases.