Leaf angle is a pivotal agronomic trait that significantly influences crop architecture and yield. Plant hormones, such as auxin, play a critical role in regulating leaf angle; however, the underlying molecular mechanisms remain to be fully elucidated. Here, we reveal that the auxin response factor gene, OsARF12, which is highly expressed in the leaf lamina joint, negatively regulates rice (Oryza sativa) leaf angle via affecting shoot gravitropism. Overexpression lines of OsARF12 exhibit more erect leaf angles, while the osarf12 mutants display enlarged leaf angles compared to the wild type. Further studies demonstrate that OsARF12 directly activates the expression of Loose Plant Architecture1 (LPA1) and LAZY1 by binding to their promoters. The osarf12 mutant presents impaired shoot gravitropism, a phenotype consistent with that of the lpa1 or lazy1 mutant. Collectively, we elucidate the biological functions of OsARF12, which modulates leaf angle through its impact on shoot gravitropism by regulating the expression levels of LPA1 and LAZY1. This study provides insight into the role of auxin in determining rice leaf angle, potentially holding profound effects for the optimization of crop architecture.