Magnetic resonance-guided radiotherapy (MRgRT) delivered with MR-linac technology represents a major advance in lung cancer radiotherapy, enabling daily online adaptive planning based on high-quality soft-tissue visualization, real-time motion assessment, and anatomy-driven treatment personalization. The challenges in lung cancer treatment with conventional radiotherapy delivery due to respiratory motion, inter and intra-fraction anatomical changes make MRgRT capabilities particularly relevant. This narrative review provides an overview of the current state of the art of MR-guided adaptive radiotherapy in lung cancer, focusing on technical foundations, adaptive workflows, and clinical implementation across different disease stages. Key aspects as patient selection, adaptive decision-making, motion management strategies, and integration into routine clinical practice are discussed. Finally, emerging clinical applications and future directions—including adaptive dose personalization and integration of functional imaging—are outlined, highlighting the potential role of MR-linac–based adaptive radiotherapy as a platform for precision radiotherapy in lung cancer.