Flash Spark Plasma Sintering (FSPS) was used to rapidly sinter pure titanium diboride (TiB2). A pre-sintered sample (Ø ​= ​20 ​mm with relative density 60%) was crossed under a current of 2–2.5 ​kA flowing entirely across the sample. The samples were locally densified up to 98% of relative density in a very short time of 20 ​s. The rapid heating (≈6000 ​°C/min) prevented the complete evaporation of B2O3, leading to the formation of rarely seen segregation of boron at the grain boundaries. Compared to SPS or hot press, the rapid FSPS processing promoted the formation boron rich grain boundaries during sintering, thus enhancing consolidation. The FSPS approach might be suitable to consolidate other refractory borides. Display omitted •Titanium diboride was successfully sintered by FSPS in less than 40 ​s.•The die-less configuration could enable an automated sintering process.•The consolidation was achieved using a low voltage (9 ​V) and a minimal energy input.•The formation of B liquid phase from B2O3 impurities accelerated the densification.