  In these lecture notes, I review how to use large N techniques to solve
quantum field theories in various dimensions. In particular, the case of
N-dimensional quantum mechanics, non-relativistic cold and dense neutron
matter, and scalar field theory in four dimensions are covered. A recurring
theme is that large N solutions are fully non-perturbative, and can be used to
reliably access quantum field theory for parameter regions where weak-coupling
expansions simply fail.
