evangelist

Concise Oxford English Dictionary © 2008 Oxford University Press:
evangelist/ɪˈvanʤəlɪst/

▶noun

• 1 a person who seeks to convert others to the Christian faith, especially by public preaching.

• 2 the writer of one of the four Gospels (Matthew, Mark, Luke, or John).

• 3 a zealous advocate.

– derivatives
evangelism noun,
evangelistic adjective.