Axiom na farko na Euclid, wanda kuma aka fi sani da "axiom of existence" ko "axiom of points," wata ka'ida ce ta asali a cikin ilimin lissafi da ke cewa:"Maki biyu suna ƙayyade madaidaiciyar layi na musamman." Wannan yana nufin cewa idan aka yi la'akari da kowane nau'i biyu daban-daban a cikin jirgin sama, akwai madaidaiciyar layi daya kuma daya tilo da ke ratsa su. Wannan axiom shine ginshiƙi na duk nau'ikan lissafi na Euclidean kuma ana ɗaukarsa a matsayin bayyananne, ko kuma zato "hankali gama gari". Shi ne mafarin ginin gaba dayan tsarin lissafi.