第一次梵蒂冈大公会议（拉丁语：Concilium Vaticanum Primum）于1868年6月29日由罗马教宗庇护九世召开，是罗马天主教会第20次大公会议，共744位教会领袖出席。会议于1869年12月8日在圣伯多禄大殿开始举行，会议讨论范畴包括：理性主义、唯物论、自由主义、教宗无误论（Papal Infallibility，指教宗在公告信仰教理上的不能误，而非教宗永远正确）等。1870年9月，由于罗马被并入意大利王国，庇护九世退缩至梵蒂冈城堡内作为抗议，会议于1870年10月20日宣告中断。此后90年间会议一直处于休会状态，直到1960年由教宗若望二十三世正式举行闭幕式。

The Vatican Council (Latin:Concilium Vaticanum Primum) was convoked by Pope Pius IX on 29 June 1868, after a period of planning and preparation that began on 6 December 1864. This, the twentieth ecumenical council of the Catholic Church, held three centuries after the Council of Trent, opened on 8 December 1869 and adjourned on 20 October 1870. Unlike the five earlier General Councils held in Rome, which met in the Lateran Basilica and are known as Lateran Councils, it met in the Vatican Basilica, hence its name. Its best-known decision is its definition of papal infallibility, strongly promoted by the Archbishop Luigi Natoli.