Streptococcus mutans is a bacterium involved in the formation of caries. Red ginger essential oil is extracted from rhizomes, has a content of natural compounds, and is used in medicine for antibacterial, anti-inflammatory, and anticancer. To prove the effect of red ginger essential oil on Streptococcus mutans bacteria. The agar diffusion method is performed to test antimicrobial activity and determine the Minimum Inhibitory Concentration (MIC) against Streptococcus mutans. Furthermore, the adherence test of Streptococcus mutans bacteria was carried out using a spectrophotometer l = 570nm. MIC red ginger essential oil against Streptococcus mutans bacteria at concentrations of 0.78% and 1.56%. In the 0.78% concentrate, an adherence value of 2.12 was obtained and in the 1.56% concentrate, an adherence value of 1.93 was obtained and 3.125% concentrate obtained an adherence value of 1.78. Red ginger essential oil has potential as an antimicrobial agent by inhibiting the adherence of Streptococcus mutans bacteria.