The chapters in this monograph present topics ranging from recent algorithmic developments to demanding applications that showcase the power of current quantum Monte Carlo methodologies. New challenges including the treatment of spin, non-adiabatic effects, non-bonded interactions, and entanglement estimation are also presented along with a perspective on the state of the field. Quantum Monte Carlo methods have proved to be very successful in calculations of many-body quantum systems. The number of applications, as well as a variety of algorithms, is growing despite the fact that the fermion sign problem imposes a significant and fundamental challenge on the efficiency of stochastic approaches in general. Quantum Monte Carlo methods allow for the solution of the many-body problem with advantageous scaling properties compared to variational basis set approaches. Both fermionic and bosonic systems can be tackled in order to obtain ground state properties or ensemble averages in the context of statistical mechanics.