The genome sequence of *Streptococcus mutans* UA159, a cariogenic dental pathogen, has been fully sequenced and reveals a 2,030,936 base pair circular chromosome with 1,963 open reading frames (ORFs), 63% of which have assigned functions. The genome provides insights into how *S. mutans* adapts to the oral environment through resource acquisition, defense against host factors, and maintaining its niche. It has a wide range of carbohydrate metabolism via nonoxidative pathways, with transport systems accounting for nearly 15% of the genome. Virulence factors include extracellular glucan production, adhesins, acid tolerance, proteases, and putative hemolysins. The strain is naturally competent and contains genes for competence and quorum sensing. Mobile genetic elements, including a conjugative transposon and a composite transposon with genes for gramicidin/bacitracin synthesis, are prominent in the genome. No bacteriophage genomes are present. *S. mutans* is the leading cause of dental caries worldwide and is associated with various oral and non-oral infections. The genome analysis shows that *S. mutans* can metabolize a wide variety of carbohydrates, surpassing other Gram-positive organisms. It possesses genes for transport and metabolism of numerous sugars and sugar alcohols, and has a complete glycolytic pathway. The organism can survive in acidic environments, which contributes to dental caries. It has an incomplete TCA cycle and can synthesize amino acids. The genome contains genes for various transport systems, including ABC transporters, and multiple proteases involved in virulence and host tissue degradation. The genome also includes genes for acid tolerance, stress responses, and other virulence factors. The presence of mobile genetic elements suggests a dynamic genome that may contribute to its adaptability and pathogenicity. The complete genome sequence provides a foundation for understanding the genetic basis of *S. mutans* pathogenicity and could lead to new strategies for preventing and treating dental caries.The genome sequence of *Streptococcus mutans* UA159, a cariogenic dental pathogen, has been fully sequenced and reveals a 2,030,936 base pair circular chromosome with 1,963 open reading frames (ORFs), 63% of which have assigned functions. The genome provides insights into how *S. mutans* adapts to the oral environment through resource acquisition, defense against host factors, and maintaining its niche. It has a wide range of carbohydrate metabolism via nonoxidative pathways, with transport systems accounting for nearly 15% of the genome. Virulence factors include extracellular glucan production, adhesins, acid tolerance, proteases, and putative hemolysins. The strain is naturally competent and contains genes for competence and quorum sensing. Mobile genetic elements, including a conjugative transposon and a composite transposon with genes for gramicidin/bacitracin synthesis, are prominent in the genome. No bacteriophage genomes are present. *S. mutans* is the leading cause of dental caries worldwide and is associated with various oral and non-oral infections. The genome analysis shows that *S. mutans* can metabolize a wide variety of carbohydrates, surpassing other Gram-positive organisms. It possesses genes for transport and metabolism of numerous sugars and sugar alcohols, and has a complete glycolytic pathway. The organism can survive in acidic environments, which contributes to dental caries. It has an incomplete TCA cycle and can synthesize amino acids. The genome contains genes for various transport systems, including ABC transporters, and multiple proteases involved in virulence and host tissue degradation. The genome also includes genes for acid tolerance, stress responses, and other virulence factors. The presence of mobile genetic elements suggests a dynamic genome that may contribute to its adaptability and pathogenicity. The complete genome sequence provides a foundation for understanding the genetic basis of *S. mutans* pathogenicity and could lead to new strategies for preventing and treating dental caries.