Yarjejeniyar muhalli ta ƙasa da ƙasa ko wani lokacin ƙa'idar muhalli, wani nau'in yarjejeniya ce da ke daure a cikin dokokin ƙasa da ƙasa, ba su damar cimma burin muhalli . A wasu kalmomi, "takardar gwamnati ce da aka yi niyya a matsayin doka ta doka tare da manufar da aka bayyana ta farko ta hana ko sarrafa tasirin ɗan adam akan albarkatun ƙasa." Yarjejeniyar tsakanin al'ummomi biyu ana kiranta da yarjejeniyar muhalli ta biyu . Idan an yi yarjejeniya tsakanin ƙasashe uku ko fiye, ana kiranta yarjejeniyar muhalli ta multilateral (MEA). Irin waɗannan yarjejeniyoyin, waɗanda Majalisar Ɗinkin Duniya ke samarwa da farko, sun ƙunshi batutuwa kamar manufofin yanayi, manufofin ruwa, sharar gida da manufofin abubuwa, muhallin ruwa, manufofin kiyaye yanayi, gurɓataccen hayaniya da amincin nukiliya. An fara amfani da yarjejeniyoyin mahalli da yawa a cikin shekara ta 1857, lokacin da yarjejeniyar ƙasar Jamus ta tsara kwararar ruwa daga tafkin Constance zuwa Austria da Switzerland . Ka'idojin muhalli na kasa da kasa sun bayyana a cikin mulkin muhalli bayan matsalolin muhalli masu iyaka da iyaka sun zama sananne a cikin shekara ta 1960s.