Evangelism is the practice of attempting to convert people to a religion. The term is used most often in reference to Christianity and Islam, since those two religions mandate that their followers make efforts to recruit as many people as possible into their faith. However, the term may be used for the practice of attempting to convert people to any religion, even if that religion does not specifically require that its followers engage in evangelism. For this reason, there are "evangelists" in Judaism, Buddhism, Hinduism, and other religions, even though those religions are not "evangelical" by nature. The term is sometimes used as a metaphor in a non-religious context as well.

The intention of most Christian evangelism is to convert those who do not follow the Christian God to Christianity for the purpose of effecting eternal salvation. Evangelism is done in obedience to the Great Commission, a command from Jesus to his disciples to proselytise, according to accounts in the New Testament. Christians who specialise in evangelism are known as evangelists, whether they are in their home communities or acting as missionaries in the field. Some Christian traditions consider evangelists to be in a leadership position, and they may be found preaching to large meetings, and in governance roles. Christian groups who actively encourage evangelism are sometimes known as evangelistic or evangelist.

The communication of Christian faith to new geographical areas and cultures is often referred to as evangelization, or specifically, world evangelization.