Lectures on Lagrangian torus fibrations.

This is a book aimed at graduate students and researchers in symplectic geometry, based on a course I taught in 2019. The primary message is that the base of a Lagrangian torus fibration inherits an integral affine structure, which you can use to "read off" a lot of interesting geometry of the total space. Topics covered include: action-angle coordinates, symplectic reduction, toric manifolds, visible and tropical Lagrangians, almost toric systems, Milnor fibres of cyclic quotient singularities, mutation of polygons, non-toric blow-up, an almost toric view on Lisca's classification of fillings of lens spaces, resolutions of cusp singularities, Markov triples and Vianna tori. The book ends with a short list of open problems. Throughout there is an emphasis on examples and there are some exercises with solutions.