What is the origin of Christianity?

Jesus’ apostles were the first Christians.

It began in modern day Israel and the surrounding areas where Jesus went gathering followers. It spread afterward throughout West Asia and Southern Europe and beyond as his apostles went about starting churches and preaching the gospel.

http://video.google.com/videoplay?docid=5216975979627863972

If you would like to know about the birth of the church (at least, the way it’s told on the bible), you could check out Acts 1 and 2

Long story short: all the apostles where gathered together in Pentecost, tongues of fire descended upon them, Peter addresses a crowd, about three thousand people are baptized, Peter emerges as the father of the church (first pope)

…and…regarding to “where”, you may want to check these maps:

Expansion of the christian church

The expansion of the early christian church

Christianity began with something that didn’t have a name at the time; Schizophrenia.

But seriously, from my reading, the ideas seem like a cross between Judaism and Greek Mythology/Philosophy with a dash of whatever the political norm was at the time.

This was the best explanation I’ve seen/heard:
http://tinyurl.com/26n5uh

ZEITGEIST, The Movie google it, watch all 3 parts.

In a sense, Christianity began long before Christ entered the scene. Old Testament prophets spoke of the coming of the Messiah, etc. However, while Christians claim these prophets are theirs, so do the Jews, and the Jews would be quick to say that Jesus was not the Messiah the Old Testament prophets spoke of. So it is difficult in a technical way on a Q&A website like this is to answer your question.

A satisfactory answer that I think most Christians and non-Christians would agree with is that its origins were in the person of Jesus Christ. His ministry inaugurated the Christian movement. No matter the denomination, I think it’s safe to say all Christians would agree that Jesus is the beginning of Christianity, not the apostles.

Personally, I hold to the Old Testament origin of Christianity. It is possible to claim that Jehovah of the Old Testament is Jesus Christ in the New. But historically speaking with no religious faith involved… Jesus’ first sermons mark the origin of Christianity, plain and simple.