3D printing technology has started to take hold as an enabling tool for scientific advancement. Born from the marriage of computer-aided design and additive manufacturing, 3D printing was originally intended to generate prototypes for inspection before going to full industrial production. As this field has matured, its reach into other applications has expanded, accelerated by its ability to generate three-dimensional objects with complex geometries. Chemists and chemical engineers have begun to take advantage of these capabilities in their own research. Certainly, the most prominent examples of this adoption have been the design and use of 3D printed reaction containers and flow devices. The focus of this review, however, is on 3D printed objects whose chemical reactivities are of primary interest. These types of objects have been designed and used in catalytic, mechanical, electronic, analytical, and biological applications. Underlying this research are the efforts to add chemical functionality to standard printing materials, which are often inert. This review details the different ways in which chemical reactivity is endowed to printed objects, the types of chemical functionality that have been explored in the various printing materials, and the reactions that are facilitated by the final printed object. Finally, the review discusses new avenues for the development and further sophistication of generating chemically active, 3D printed objects.