  We present an introduction to ab initio nuclear theory with a focus on
nuclear reactions. After a high-level overview of ab initio approaches in
nuclear physics, we give a more detailed description of the no-core shell model
technique equivalent to a large extent to configuration-interaction methods
applied in quantum chemistry. We then introduce the no-core shell model with
continuum approach that provides a quantum many-body description of nuclear
reactions. After a brief review of nuclear reactions important for
astrophysics, we present examples of results of ab initio calculations of
radiative capture and transfer reactions in light nuclei.
