Anonymous Christian is the controversial Christian doctrine concerning the fate of the unlearned which was introduced by the Jesuit theologian Karl Rahner (1904–1984) that declares that all individuals, who sincerely seek truth and goodness, and strive to follow the moral truths they know, can respond positively to God's grace, albeit unknowingly or indirectly, even if they do so through other religious traditions and/or are not explicitly aware of Jesus Christ. In other words, God's grace, including the benefits of Christ's sacrifice, are not confined to the boundaries of any particular religious tradition or by our awareness or acceptance of Christian doctrine. Instead, anyone who lives a life of love and goodness, guided by the moral teachings found in Christianity, even if they do not consciously identify with it, is implicitly united with Christ and can be saved through him, implying that non-Christians can still be recipients of God's grace and attain salvation.

Non-Christians could have "in [their] basic orientation and fundamental decision," Rahner wrote, "accepted the salvific grace of God, through Christ, although [they] may never have heard of the Christian revelation."

The notion of inclusivism, for which Rahner's Anonymous Christian is the principal Christian model, is "perhaps the most popular of interreligious postures" and was one of the most influential theological ideals to affect the Second Vatican Council.

Karl Rahner accepted the notion that without Christ it was impossible to achieve salvation, but he could not accept the notion that people who have never heard of Jesus would be condemned.

"Anonymous Christianity" means that a person lives in the grace of God and attains salvation outside of explicitly constituted Christianity. A Protestant Christian is, of course, "no anonymous Christian"; that is perfectly clear. But, let us say, a Buddhist monk (or anyone else I might suppose) who, because he follows his conscience, attains salvation and lives in the grace of God; of him I must say that he is an anonymous Christian; if not, I would have to presuppose that there is a genuine path to salvation that really attains that goal, but that simply has nothing to do with Jesus Christ. But I cannot do that. And so if I hold if everyone depends upon Jesus Christ for salvation, and if at the same time I hold that many live in the world who have not expressly recognized Jesus Christ, then there remains in my opinion nothing else but to take up this postulate of an anonymous Christianity.

Rahner acknowledges the sinful state of humanity and emphasizes that salvation is not something humanity deserves but is freely given by God's grace. Rahner's view can therefore be compatible with the Protestant principles of "sola gratia" ("by grace alone"), "sola fide" ("through faith alone"), and "solus Christus" ("in Christ alone"), as he affirms that Jesus Christ is the unique and definitive mediator between God and humanity, and that it is only through His life, death, and resurrection that salvation is made possible. Rahner asserts that the grace obtained through his sacrifice is universally available to all people, so that even those who are not explicitly Christian can benefit from his saving work and be saved through their implicit faith in him.

According to Rahner, a person could "intellectually profess disbelief but [be] existentially ... committed to those values which for the Christian are concretized in God." Rahner suggests that God's grace is at work in the lives and hearts of all people, drawing them to himself, prompting them to turn away from wrongdoing, transforming them from within, and offering opportunities to lead them toward salvation, even if they are not consciously aware of it. Individuals who also do not profess belief in Jesus, even if the Gospel has been presented to them, may also be included in the scope of Jesus' salvific work due to their responding positively to God's grace through their moral and spiritual striving which serves as evidence of God's work in their lives. The ultimate determinant of salvation in this view, is one's response to God's grace which enables individuals to respond positively to these impulses/promptings of the Holy Spirit and attain salvation.

The theologians W. D. Davies and Dale Allison wrote that proponents of the notion find scriptural support in Romans 2:14–16, as well as in Matthew 25:31–46.