Monolithic ZrB2 belongs to the family of the ultra-high-temperature ceramics well-known for its ultra-refractoriness, high thermal and electrical conductivities, and elevated hardness.  They make it to be also a suitable candidate for tribological applications requiring wear resistance. However, its poor densification by classical sintering from commercial ZrB2 powders is a limiting factor for its widespread use in tribological applications. Consequently, in the present study the reactive spark plasma sintering (R-SPS) of ZrB2 ceramics have been investigated. To this end, ZrH2+2B powder mixtures were subjected to high-energy pre-ball-milling (in the form of shaker milling). The results proved that this approach is much more effective in obtaining fully-dense, medium-grained, hard ZrB2 ceramics than (i) the R-SPS of simply-mixed ZrH2+2B powder mixtures, (ii) the SPS of commercial ZrB2 powders, and (iii) SPS of ZrB2 also subjected to high-energy pre-ball-milling. Additionally, we have also investigated the unlubricated tribological behaviour of the optimally R-SPSed ZrB2 ceramic against diamond, demonstrating that it is a promising tribo-ceramic for engineering applications requiring wear resistance.