The research entitled the effectiveness of online learning on the learning outcomes of elementary school students, while the purpose of this study was to obtain information about the effectiveness of online learning on student achievement, especially in grades IV and V. This research was conducted at Al Ikhlas Islamic Elementary School. South Jakarta. Indonesia. The method used in this study is a quantitative descriptive approach, the instrument used as an indicator to explore the effectiveness of online learning by using a questionnaire as an instrument. The population this study were students in grades IV A, IV B, V A, VB and VC who were taken randomly, totaling 94 respondents using random sampling. Data analysis used a simple linear regression test with a significant level of 0.05 (5%). Based on the results of the calculation of a significant value of 0.000<0.05, it can be concluded that the effectiveness of online learning on student achievement has a regression equation, this is proven by the results of statistical tests using the Ttest and the calculation results obtained are 11,064>1,661, with significance level 0.000<0.05.While the effectiveness of online learning on student achievement is obtained a value of 75.6% through the calculation of the coefficient of determination. The results of this study indicate that there is quite a significant or low influence on online learning on student achievement.