In Christian theology, baptism with the Holy Spirit, also called baptism in the Holy Spirit or baptism in the Holy Ghost, has been interpreted by different Christian denominations and traditions in a variety of ways due to differences in the doctrines of salvation and ecclesiology. It is frequently associated with incorporation into the Christian Church, the bestowal of spiritual gifts, and empowerment for Christian ministry. Spirit baptism has been variously defined as part of the sacraments of initiation into the church, as being synonymous with regeneration, as being synonymous with Christian perfection that empowers a person for Christian life and service. The term baptism with the Holy Spirit originates in the New Testament, and all Christian traditions accept it as a theological concept.

Prior to the 18th century, most denominations believed that Christians received the baptism with the Holy Spirit either upon conversion and regeneration or through rites of Christian initiation, such as water baptism and confirmation. Emerging in the mid-18th century, Methodism (inclusive of the holiness movement) affirms the possibility of entire sanctification as a second work of grace, which it teaches is the baptism of the Holy Spirit. In the 20th century that saw the spread of Pentecostal churches, which identified baptism of the Holy Spirit with glossolalia, the belief that this is an experience distinct from Christian initiation has come into increasing prominence.