Understanding the evolution and deaths of massive stars is central to solving major open questions in astrophysics. Massive stars shape galaxies through ionizing radiation and chemical enrichment, while their explosive ends inject energy and heavy elements into the interstellar medium. Their remnants—neutron stars and black holes—are key sources of gravitational waves and high-energy phenomena. Yet, crucial aspects of massive star evolution, explosion mechanisms, and remnant formation remain elusive. We still lack a clear mapping between transient phenomena and progenitor systems, and a predictive framework for which stars produce which types of supernovae and which collapse directly to black holes. Recent advances have brought us to a pivotal moment. Time-domain surveys are capturing early-phase supernovae and revealing dramatic late-stage behavior of progenitors. Gravitational-wave detections are shedding light on compact object formation. Massive star surveys are mapping the crucial role of binarity in massive star evolution and death. Upcoming facilities will open new discovery spaces in stellar evolution and explosion physics. During this program we hope to shed light on interconnected problems in the massive stars and supernovae by creating space for cross-disciplinary dialogue.