Searches for new phenomena in hadronic final states using the ATLAS detector

Many theories beyond the Standard Model predict new phenomena giving rise to multijet final states. These jets can originate from the decay of heavy resonances into Standard Model quarks or gluons, or from more complex decay chains involving dark-sector particles. Also of interest are resonant and non-resonant hadronic final states where jets stem from a dark sector, leading to a diverse phenomenology depending on the interactions between dark and visible particles. This contribution summarises recent ATLAS results based on 13 TeV Run 2 data, highlighting three complementary analyses targeting boosted light resonances, flavour-violating dark matter, and semi-visible jets.