洗礼（或称浸礼、圣洗圣事、受洗），是一宗教仪式，现普遍指基督教的传统仪式。据《圣经》记载，施洗约翰曾为耶稣施洗（浸），而这亦是耶稣吩咐的仪式。洗礼一词来自希腊文「Βάπτισμα」（Baptisma），原意是进入水中或沉入水中。部分基督教教派将洗（浸）礼列为圣事之一。

洗礼通过把祝圣过的水倒在、撒向受洗者头上；或把受浸者放进水中，然后扶起来施行。现天主教、东正教和大部分新教教派实施的婴儿洗礼，在2世纪时已有文献记录，教父指出是使徒传统。由于对洗礼有不同的理解，因而形成不同的宗派；不同的宗派内，在基督教历史上也发展出不同的教义。对于洗礼的讨论，主要提到：洗礼的性能，施洗的方法及婴孩、死人受洗等问题。

Baptism (from the Greek noun βάπτισμα baptisma; see below) is a Christian sacrament of admission and adoption, almost invariably with the use of water, into the Christian Church generally. The canonical Gospels report that Jesus was baptized—a historical event to which a high degree of certainty can be assigned. Baptism has been called a sacrament and an ordinance of Jesus Christ. In some denominations, baptism is also called christening, but for others the word "christening" is reserved for the baptism of infants. Baptism has also given its name to the Baptist churches and denominations, they being called Baptism as a whole.