Reducing income inequality is a critical factor in ensuring a nation's overall well-being. Economic inequality refers to the unequal income distribution between the wealthy and the poor, creating a disparity where the rich become wealthier while the poor face increasing financial hardships. Understanding the factors that contributing to income inequality is essential for working toward the nation's ideals. This study focuses on analyses income inequality in developing Muslim countries, specifically among five member states of the Organization of Islamic Cooperation (OIC), to provide insights into this pressing issue. This study uses a quantitative research methodology to investigate the influence of education, unemployment, poverty, and the Islamic Human Development Index (I-HDI) on the Gini coefficient in five OIC member countries between 2018 and 2022, It relies on secondary data obtained from the World Bank, Our World in Data, INDP, and ILO Stat.Time series techniques are employed to analyse the data. The study population consists of five OIC member countries. Data analysis involves descriptive statistics, classical assumption tests, and panel data regression analysis, conducted using EViews 12 software. The F-test results from this study reveal that education, unemployment, poverty, and the Islamic Human Development Index (I-HDI) collectively influence the Gini coefficient. Based on these findings, the study offers several recommendations. First, future research should incorporate additional variables to explore other relevant factors affecting income inequality. Second, broader analyses encompassing all OIC member countries are encouraged, given the limited number of studies that use OIC countries as both the population and sample. These efforts could provide deeper insights and enhance the understanding of income inequality dynamics within the OIC.