ALBINO3 (ALB3) protein functions in the insertion and assembly of thylakoid membrane protein complexes and plays a critical role for chloroplast development in . However, the biological function of ALB3 homologs in rice, OsALB3, remains elusive. Here, we identified a rice mutant, (), that displayed yellow leaves and died at the seedling stage. The content of chlorophyll in , compared with wild type, was significantly decreased. Transmission electron microscopy observation shows that the chloroplast of lacks thylakoid membranes. The causal mutation, which is located in , was isolated by Mutmap+ combined with a simple mutation filtering process. Knockout of leads to yellow leaves and seedling lethality, mimicking the phenotype of . is widely expressed and OsALB3 is chloroplast-localized. Moreover, the content of light-harvesting chlorophyll-binding proteins in is reduced. Together, our study demonstrated the essential role of OsALB3 in chloroplast development and provided clues to the possible conserved molecular function of ALB3 in rice.