Papa Gregori IV alikuwa Papa kuanzia mnamo Septemba 827 au tarehe 29 Machi 828 hadi kifo chake tarehe 25 Januari 844. Alitokea Roma, Lazio, Italia. Alimfuata Papa Valentino akafuatwa na Papa Sergio II. Orodha ya Mapapa https://www.vatican.va/content/vatican/en/holy-father.index.html#holy-father https://www.vatican.va/content/vatican/en/holy-father.index.html#holy-father Papa Gregori IV katika Kamusi Elezo ya Kikatoliki