I think it is a pre-scientific method of making sense of the world around us. I don't believe the early founders of the world's religions had evil, or manipulative goals in mind. They were just trying to figure things out. Of course, religion has been subverted by those who do have evil intentions of control.

Seriously, the true purpose of religion is to control the population.

Emile Durkheim, the founder of sociology, famously said that religion was "society worshipping itself" symbolically. For him, religion existed to promote social solidarity, to keep the society together, and everyone on the same page. Karl Marx said that religion was the capitalists' way of distracting workers from their oppressed and overworked condition by promising that their reward would be in the afterlife. Economic anthropologist Marvin Harris feels religion is there to keep the local ecology and economy in line, and that "primitive" religious practices really serve other purposes. For example the Hindu prohibition on killing cows makes ecological sense because you can feed more people longer on the milk, butter, and cheese that a living cow produces than if you killed it and ate its meat. Those are the major social science perspectives on it. There are more, but I don't want to write a novel.

I've always believed it was a very deliberate means of controlling the masses, and maintaining power for those who insisted on having it.
It may have started off as a way for the ancients to explain what they didn't understand, but once those in power learned they could use it to control the people around them, they knew they could never let it go.

The concept of “Gods” began as an attempt to explain the unexplainable. As beliefs deepened and became entrenched, kings and other elevated men leverage these “beliefs” to control the gullible

A lot of the responses here aren't giving religion what I think should be sufficient credit.

For starters, what do you mean by "true"? Original? Current? Predominant usage, or any usage? That's as vague as asking what is the purpose of life.

By asking the question, you even assume that religion has a purpose. I think that purpose assumes intent, and intent assumes conscious design. I'm not sure that any of those things are necessarily true. Something can exist without having a purpose.

Religion was an incredibly potent and important societal mechanism within humanity's social evolution. It was the main driver of growing beyond our tribal and communal beginnings, allowing peoples of disaparate cultures to cooperate at levels unheard of at the time. The first cities and kingdoms revolved around this concept. Yet, in this modern world, where the observable both macro and micro, are mostly defined, religion is archaic. I liken it to the idea of the appendix; useful in our past, but a problem for our present. The modern world is so far beyond the need for it, that it creates more social negatives than positives.

To delude, divide, confuse, and control.

Just about any organization attracts people who, for some reason, want to be in charge. It’s a big ego-boost I suppose, and it can be irritating. Yet those controlling people are useful. They exist for reasons. Some of them learn to moderate their egos and develop into true leaders.

It’s not just churches. The same phenomenon occurs in businesses, in government, and in social organizations. Maybe those controlling folks are eldest siblings. WAIT! That’s not very tactful. Disregard that.

I Am not in accord with the tenets of Christianity as presented by traditional churches, but I do believe that Christian Churches serve a valuable purpose to those who belong. As skado says, religion provides a means whereby people can learn to live fully and joyfully.

Much church dogma is pure rot IMO, and I have thrown it out. Like skado, I threw out the bath water but kept the baby. For me the baby is awareness, awe, appreciation, courage, and joy.

control

I think the truest purpose - was convincing men to die willingly in warfare. The promise of a glorious afterlife was an effective incentive.

I would think it was originally just a way to explain nature. Then people saw how they can control others through it.

The discipline you are trying to describe is called philosophy with strong emphasis on ethics. In science a PhD means Doctor in Philosophy. Philosophy and science has always been interlinked. Buddhism is considered atheist being more philosophy (self-aware) than religion. The Japanese are considered atheist because Shinto is focused on nature rather than a single deity.
When a supreme being emerges and is recognized as the head of a philosophical thinking, it becomes a religion, ceases to be objective hence it becomes a way to control the weak minded masses.

Control.

Religion was invented when the first conman met the first fool.
Market Twain

To allow people to be stupid. If you cannot think or read well or if you are just incredibly insecure, not believing yourself, then religion fills the hole. God makes you great and the devil is why you fail. No where do you come into play with rational thought.
Yes that is it. Religion removes rational thought and yes allows a government to control us via their religion and the stupid sheep.

Religion has many functions, and the inability of anti-theistic approaches to offer a full complement of alternatives is one of the reasons religions still persist despite the Enlightenment. One of these functions is the deferment of the hope of Justice.

We live in a very unfair and unjust world. Society requires that the majority of its citizens conform to preset standards. Religion offers the hope (a false hope in my opinion) that the balance of injustice will be offset at a future time. That the rich do not in fact have an unfair advantage over the poor and oppressed. A judgment awaits all.

We know these ideas are crap, but what do we offer in their place? The non-theistic community should be at the forefront of establishing justice in the here and now. We all have a responsibility to be true humanists.

I would guess; to maximize the effects of imagination. When life is harsh, which it often is, or just isn't giving us what we think we deserve; imagination is a refuge.
Like any players of D&D will tell you, it's more fun the more people who plays along with the fantasy. It feels more real the more people keep insisting it is. Some people can speak confidently and are payed - sometimes exorbitant sums - to strengthen the shared, oh so comforting, delusion where you are the hero(ine), beloved by mystical forces and all wishes will come true.

Seems obvious to me. No one who ever argued in favor of religion has failed to fall back on "wouldn't it be nice if it was true"; as if that was the whole point. As if belief is the act of picking whatever fantasy you want to be true and not what the evidence proves.

Well my opinion religion does two thing attempts to answer question we don't have answer for and secondly to control the population.

The purpose of religion is pretty much the same as the purpose for Santa Claus. Parents tell their children about Santa Claus in order to induce them to be good, so as to get on Santa's "Nice" list, and avoid the "Naughty" list.

Religion is meant to scare people -- telling them they'll go to Hell unless they do what the church leader tells them. A good church leader (okay, that may be a contradiction in terms) will focus on ethics. However, many church leaders tell their followers to give them money -- making a scam out of the Jesus myth.

Control.

It's how the first athiests controlled the gullible.

"The central act of religion is to train the individual to release ego-identity, and thereby release psychological suffering regardless of material circumstances."

You would perhaps enjoy Mircea Eliade's The Sacred and the Profane:
[amazon.com]

Eliade attempts to explore the psychological basis of religion. To greatly simplify, the main purpose is to sanctify a portion of the natural environment as known, and ordered, from which to draw emotional strength to face the rest of the unordered world.

Seems religion is a way to control every aspect of a person's life.