The outstanding performance of the LHC during Run~2 data taking let the ATLAS Experiment to collect a massive dataset of ${p}{p}$ collision at $\sqrt{s}=13$ TeV. This impressive availability of data to analyse paves the way to the research of rare events, as test of the Standard Model validity. One of the most interesting process is the production of $t\bar{t}t\bar{t}$, an ultra rare process predicted by the Standard Model and very sensitive to new physics contribution. The ATLAS experiment has targeted the measurement of this process in two separate analyses, focused in two different detection channels. These analyses led to the first evidence of $t\bar{t}t\bar{t}$ production with an observed (expected) significance of $4.7$ ($2.6$) standard deviations in their combination.