Flavour Physics Beyond the Standard Model

Flavour physics plays a central role in the search for physics beyond the Standard Model, posing fundamental questions whose answers may point to new physics scales far above the electroweak scale. The flavour structure of the Standard Model is strikingly hierarchical, hinting at underlying organizing principles yet to be uncovered. At the same time, flavour-changing processes rank among the most sensitive probes of new physics. In this chapter, we review how precision measurements of flavour-violating observables, in particular meson-antimeson mixing and rare decays, provide powerful indirect tests of new physics, constraining scenarios from heavy mediators to light, weakly coupled particles. We also survey theoretical frameworks proposed to explain the origin of the Standard Model flavour hierarchies. Together, these complementary aspects demonstrate how flavour physics continues to shape both experimental strategies and theoretical developments in the quest to understand the fundamental structure of particle interactions.