Composites play an important role as structural materials in a range of engineering fields due to their potential to combine the best mechanical properties of their constituents. In biology, composites are ubiquitous and exhibit fascinating and precise architectures at fine length scales; bone, hexactinellid sponges and nacreous abalone shells are prime examples. Here, typical biological composite topologies are emulated with multi-material 3D printing at micrometer resolution. From base materials that are brittle and exhibit catastrophic failure, synthetic composites are created with superior fracture mechanical properties exhibiting deformation and fracture mechanisms reminiscent of mineralized biological composites. This complementary computational model predictions of fracture mechanisms and trends in mechanical properties are in good agreement with the experimental findings. The reported findings confirm that specific topological arrangements of soft and stiff phases as a design mechanism enhances the mechanical behavior in composites. This study demonstrates 3D printing as a means to create fracture resistant composites. Moreover, these results indicate that one can use computer models to design composite materials to exhibit tailored fracture properties and then use 3D printing to synthesize materials with such mechanical performance.