Acide ya fosifori, izwi kandi nka acide orthophosifike, ni aside idasanzwe ikoreshwa cyane mu nganda zitandukanye. Ifite aside irike igereranije, formulaire yimiti ni H3PO4, naho uburemere bwa molekile ni 97.995. Bitandukanye na acide ihindagurika, aside fosifike irahagaze kandi ntisenyuka byoroshye, bigatuma ihitamo kwizewe mubikorwa bitandukanye. Mugihe aside fosifike idakomeye nka hydrochlorike, sulfurike, cyangwa acide nitric, irakomeye kuruta acide na boric. Byongeye kandi, iyi aside ifite imiterere rusange ya acide kandi ikora nka acide ya tribasic idakomeye. Birakwiye ko tumenya ko aside ya fosifori ari hygroscopique kandi byoroshye gukuramo ubuhehere buturuka mu kirere. Byongeye kandi, ifite ubushobozi bwo guhindura aside pyrophosifike iyo ishyushye, kandi gutakaza amazi nyuma birashobora kuyihindura aside metafosifike.