  Despite the established role of additive manufacturing (AM) in aerospace and
medical fields, its adoption in astronomy remains low. Encouraging AM
integration in a risk-averse community necessitates documentation and
dissemination of previous case studies. The objective of this study is to
create the first review of AM in astronomy hardware, answering: where is AM
currently being used in astronomy, what is the status of its adoption, and what
challenges are preventing its widespread use? The review starts with an
introduction to astronomical instruments size/cost challenges, alongside the
role of manufacturing innovation. This is followed by highlighting the
benefits/challenges of AM and used materials/processes in both space-based and
ground-based applications. The review case studies include mirrors,
optomechanical structures, compliant mechanisms, brackets and tooling
applications that are either in research phase or are implemented.
