TASI Lectures on Future Colliders

These lectures review the main motivations for future high-energy colliders, focusing on the understanding of electroweak symmetry breaking and on the search for physics beyond the Standard Model. The open questions and the challenges are common to all future projects; for concreteness, I will use studies of the potential of ${\mathrm{e}}^{+}{\mathrm{e}}^{-}$ and pp circular colliders to provide examples of the anticipated physics reach.