This Workshop is the eleventh conducted by the Simons Center for Geometry and Physics at Stony Brook and the Sixteenth in the series Simons Summer Workshops. One of the predictions of string theory is that certain apparently consistent quantum field theories cannot be consistently coupled to quantum gravity—they do not arise from consistent string vacua. This gave rise to the notion of the “Swampland”. Recent developments, in particular the Weak Gravity Conjecture, have led to many new and much stronger restrictions which involve physicists working in many fields and give new insights into the structure of string vacua. That will be the focus of this years Summer workshop.