The formulation of the problem in this study is whether formative assessment using the Quizizz gamification application affects students' learning interest in mathematics for eleventh-grade students of SMA Negeri 2 Baubau. This study aims to determine the effect of formative assessment using the Quizizz gamification application on students' learning interest in mathematics for eleventh-grade students of SMA Negeri 2 Baubau. Data collection in this study used research instruments in the form of student response questionnaires regarding the implementation of formative assessment using the Quizizz gamification application, as well as a student mathematics learning interest questionnaire. The data obtained were analyzed using descriptive statistical analysis and inferential analysis. Based on the research results, the conclusions are as follows: Normality analysis, linearity analysis, and heteroscedasticity analysis indicate that the data are normally distributed, have a linear relationship, and show no symptoms of heteroscedasticity. The results of the analysis show that the t-value = 4.081 with a significance value of 0.000 < 0.05 and a regression coefficient = 0.480. Therefore, it is concluded that H0 is rejected and H1 is accepted, which means there is a positive and significant effect of formative assessment using the Quizizz gamification application on the learning interest of Class XI students at SMAN 2 Baubau in mathematics.