Scattering amplitudes in relativistic quantum theories possess a multitude of remarkable hidden structures and correspondences. They are of vital importance for high-precision comparisons of theory and experiment at the LHC, yet they also have the promise of revealing fundamentally new approaches to quantum field theory and of exposing interrelations that unify gauge theories, gravity, and string theory. This workshop will provide a meeting ground to communicate the current themes and recent progress in various areas of theoretical physics touched by scattering amplitudes. This includes N = 4 SYM, higher-loop QCD, perturbative gravity, string amplitudes, polylogarithms, Grassmannians and the amplituhedron, soft theorems, twistor strings, color-kinematics duality and double-copy properties of gravity, supergravity UV behavior, and more.