High-energy physics stands at a pivotal moment, poised between extraordinary recent advancements and the technological and conceptual challenges of probing ever deeper into the universe. This colloquium will present the scientific drivers motivating the next generation of particle colliders—from precision studies of the Higgs sector to the search for new particles and interactions beyond the Standard Model. We will examine the landscape of proposed machines, including high-luminosity and high-energy hadron colliders, next-generation lepton colliders, highlighting their potential to transform our understanding of fundamental physics.