Layin Longitude, wanda kuma aka sani da meridian, wani layi ne na hasashe a saman duniya wanda ya haɗu da Poles na Arewa da Kudu kuma yana auna tazarar wuri gabas ko yamma da Prime Meridian, wanda shine layi na sabani wanda ya ratsa ta. Royal Observatory a Greenwich, London, Ingila. Ana bayyana Longitude a cikin darajoji, mintuna, da daƙiƙa, tare da digiri 360 na Longitude wanda ya cika cikakkiyar da'irar duniya. Layin Longitude a digiri 0 shine Prime Meridian, kuma kishiyar layin dogon a digiri 180 shine Layin Kwanan Wata na Duniya.