Masallacin Sultan Ahmed (Baturke: Sultan Ahmet Camii), wanda kuma aka sani da Masallacin Blue, masallaci ne na Masarautar da ke Istanbul, Turkiya. Masallaci mai aiki, yana kuma jan hankalin ɗimbin baƙi. An gina shi tsakanin 1609 zuwa 1616 a lokacin mulkin Ahmed I. Its Külliye ya ƙunshi kabarin Ahmed, madrasah da asibitin. Fale-falen fale-falen da aka yi da hannu yana ƙawata bangon ciki na masallacin, kuma da daddare ana yi wa masallacin wanka da shudi yayin da fitilu ke kan manyan rumfunan masallacin guda biyar, mininare shida da manyan gidaje takwas. Yana zaune kusa da Hagia Sophia, babban masallacin Istanbul har zuwa ginin Masallacin Blue da kuma wani shahararren wurin yawon bude ido. An saka Masallacin Blue a cikin jerin wuraren tarihi na UNESCO a shekarar 1985 a karkashin sunan "Yankunan Tarihi na Istanbul". Bayan Zaman Lafiya na Zsitvatorok da babban rashi a cikin yaƙin da aka yi da Farisa a shekara ta 1603–18, Sultan Ahmed I ya yanke shawarar gina babban masallaci a Istanbul don sake ƙarfafa ikon Ottoman. Zai zama masallacin daular farko na sama da shekaru arba'in.