Missionary
A missionary is one who is sent on a mission, especially one sent to do religious or charitable work in a territory or foreign country. The Latin root from which the word "missionary" is derived is equivalent to the Greek word apostolos (^ [[Strong's](Strong's_Concordance)\ #652]^), meaning "one sent forth", from which we get "apostle". It has been defined as one who attempts to persuade or convert others to a particular faith (or set of beliefs) [1]; often an evangelist or other representative of a religious community who works among those outside of that community.
The term is most commonly used to refer to Christian missionaries, although it can generally apply to proselytizing of any creed or ideology.