宗座缺出论是一种不承认召集第二次梵蒂冈大公会议的教宗若望二十三世以来，在梵蒂冈领导罗马天主教教宗的理论。「宗座从缺」是天主教用语，指一位教宗逝世或退位后，在教宗选举选出继任者之前教宗职位的空缺状态。宗座缺出论者认为，自1958年若望二十三世上台以来，该职位就一直空缺。

总的来说，宗座缺出论者视自己为传统天主徒，他们反对第二次梵蒂冈大公会议所推行的改革，以及允许用当地语言的弥撒仪式取代传统的使用拉丁语的脱利腾弥撒。他们认为，在20世纪后半页执掌梵蒂冈的人，推行了此类变革，因而都是异端。另一些传统人士则承认自庇护十二世起的所有教宗，尽管他们个人采信了许多无耻的异教观念，还仍然是真正的教宗，因为他们都没有动用他们的教宗不能错误性（这种权利的动用十分罕见）来宣扬异端邪说，而所有的天主徒也都认为教宗不可能这幺做。

Sedevacantism is the position, held by a minority of traditionalist Catholics, that the present occupant of the Holy See is not truly pope and that, for lack of a valid pope, the see has been vacant since the death of Pope Pius XII in 1958. Sedevacantists believe that there is at present a vacancy of the Holy See that began with John XXIII (1958–63) or at latest with Paul VI (1963–78), who, they say, espoused the heresy of Modernism and otherwise denied solemnly defined Catholic dogmas and so became heretics.