Papa Julius I alikuwa Papa kuanzia tarehe 6 Februari 337 hadi kifo chake tarehe 12 Aprili 352. Alitokea Roma, Italia. Alimfuata Papa Marko akafuatwa na Papa Liberius. Anajulikana hasa kwa juhudi zake za kumaliza vurugu zilizotokana na Uario akisimama upande wa Patriarki Atanasi wa Aleksandria katika sinodi maalumu ya mwaka 342 na akidai Kanisa la Roma lilitakiwa kushirikishwa kwanza . Tangu kale anaheshimiwa kama mtakatifu. Sikukuu yake huadhimishwa kwenye tarehe ya kifo chake. Watakatifu wa Agano la Kale Orodha ya Watakatifu Wakristo Orodha ya Watakatifu wa Afrika Orodha ya Watakatifu Wafransisko Orodha ya Mapapa Mababu wa Kanisa Opera Omnia Translations of Jaffe-Kaltenbrunner's Register of the Pontiff. Archived 28 Januari 2013 at the Wayback Machine. https://www.vatican.va/content/vatican/en/holy-father.index.html#holy-father Kirsch, Johann Peter. "Pope St. Julius I." The Catholic Encyclopedia Vol. 8. New York: Robert Appleton Company, 1910. 28 September 2017. "Can you be ignorant," writes Julius, "that this is the custom, that we should be written to first, so that from here what is just may be defined" (Epistle of Julius to Antioch, c. xxii).