Christianization (or Christianisation) is a term for the specific type of change that occurs when someone or something has been or is being converted to Christianity. Christianization has, for the most part, spread through missions by individual conversions, but has also been the result of violence. Christianization is also the term used to designate the conversion of previously non-Christian practices, spaces and places to Christian uses and names. In a third manner, the term has been used to describe the changes that naturally emerge in a nation when sufficient numbers of individuals convert, or when secular leaders require those changes. Christianization of a nation is an ongoing process.
It began in the Roman Empire when the early individual followers of Jesus became itinerant preachers in response to the command recorded in Matthew 28:19 (sometimes called the Great Commission) to go to all the nations of the world and preach the good news of the gospel of Jesus. Christianization spread through the Roman Empire and into its surrounding nations in its first three hundred years. The process of Christianizing the Roman Empire was never completed, and Armenia became the first nation to designate Christianity as its state religion in 301.