Introduction: Aedes sp. is a vector of some serious diseases that attack humans. Some of them are dengue fever and dengue hemorrhagic fever. The prevention can be done by eradicate the Aedes sp. larvae, which is, the key strategies for vector control programs around the world. Organophospate (OP) insecticide themepos is a commonly used larvacidal product to control dengue vector mosquito larvae. Lately there have been reports of Aedes sp. resistance against temepos in countries such as Brazil, Cuba, El Salvador, Argentina, Bolivia, Venezuela, Peru, Colombia, and Indonesia. Therefore, need another alternative in the form of organic larvicida derived from lemongrass leaves (Cymbopogon citratus) Method: This research is a true experiment with posttest control group design. The subjects were 600 larvae of Aedes sp. instar III which were divided into 25 heads in each test group (2.5%, 2%, 1.5%, 1%, 0.5%, 0.25%, 0.1%, and 0,05%), positive control group (Abate 1%) and negative control (0%) repeated as many as 3 replications. The treatment was carried out for 12 hours and observed the number of dead larvae at each hour. Data were analyzed by statistical test of Wallis Kurskal Test followed by post-hoc test 6 Mann-Whitney Test. We also tested probit analysis to determine lethal time (LT50 and LT90) and lethal concentration (LC50 and LC90) Result: There was a significant difference (p <0.05) between all test concentrations except between 0.05% against negative control it could be evidenced that the lemongrass leaves (Cymbopogon citratus) has a larvicidal effect on Aedes sp.. The results of probit analysis for LC50 and LC90 were 3,719% and 6,246%, respectively. It is known that LT50 at concentrations of 2.5%, 2%, 1.5%, 1%, 0.5%, 0.25%, 0.1%, and 0.05% respectively are 0.3 hours, 2.3 hours, 4.9 hours, 7.7 hours, 8.8 hours, 13 hours, 20.1 hours and 21.6 hours. While the LT90 at concentrations of 2.5%, 2%, 1.5%, 1%, 0.5%, 0.25%, 0.1%, and 0.05% respectively were 7.5 hours, 9.6 hours, 12.1 hours, 15 hours, 16.1 hours, 20.3 hours, 27.4 hours and 28.9 hours. Conclusion: The ethanol extract of Lemongrass leaves Cymbopogon citratus was shown to have a larvicidal effect on Aedes sp. instar III larvae most effectifically at concentrations of 2.5% and 2% . The values of LC50 and LT50 at the end of the observations are 3.719% and 0.308 hours respectively. The values of LC50 and LT90 at the highest concentration (2.5%) were 6,246% and 7,594 hours respectively. The higher concentration of ethanol extract of lemongrass leaves Cymbopogon citratus the greater the effectiveness in killing Aedes sp. larvae.