When I was about 3 years old, my mother married her second husband. My step-father Eduardo was my hero, and he did not follow any religion, which I did not know nor would I have understood what that meant at that young age. But my catholic grandma likeD Eduardo very much, and I heard her calling him “ateo” in a half-joking way (she was not fanatical about her religion). So, if my hero was an ateo, then I am an ateo!! It started like that. Later on, when I began understanding what an atheist was, I confirmed and consolidated my conviction that I actually was an atheist. Then over the years and through getting to know the nature of christians, I have become an antitheist.

Well … I was born an atheist. At 4.6 I tried to become a Lutheran Christian … because I had been baptised by that brand, but my conversion failed miserably at age 5.17. However, given that I wasn't generating an income, I didn't declare my pocket money, I didn't go to the magistrates court to have my name official erased from the church register. I did that during the first petrol crisis in 1973. The teacher in charge of religious education walked into the classroom suggesting that the tanks should be sent into the states that refused to sell "us" their oil at bargain basement prices.
I got up and went straight to the magistrates court and applied for the eradication of my name from the Lutheran register. Naively I had been hoping to be heard by a magistrate. … I only filled in the form and a few weeks later I received the verdict telling me that I was no longer a member of the Lutheran church.
My father's uncle quit the bunch on the early 1920s, after surviving WW1 and subsequent battles on behalf of some bloody White Russian MAFIA fighting the Bolsheviks. At this time his action was almost an act of heresy.

Nothing "happened" and that is the whole point!

No specific incident. As my ability to employ critical thinking increased, my ability to believe in myths decreased.

When I was growing up religion was never really brought up in our house so I didn't really think about it at all. I guess maybe I thought we were non practicing Christians or something since everyone else around us was Christians. In middle school biology class our teacher (who was actually a tech ed teacher who was asked to teach biology because I guess they were short on teachers or something...) assigned us the very ridiculous (in my opinion) assignment to write an essay on whether or not we believed evolution was real. We had never been asked to write a similar opinion essay on any of the other concepts we had been taught and I remember turning to my friend next to me and asking "what the heck is going on with this assignment, it's weird?" and her turning back to me and saying that she thought evolution was made up and that God did it all. In that moment everything solidified in my mind, it was all bs. That assignment really backfired for that teacher whose aim was, I'm sure, to discredit the theory of evolution. I was nonreligious all along but that was the moment that it was solidified.

It was my priest actually in our one on one cathesism classes. I had many many questions about religion and the Bible.

I stumped him on the last one, about Cain, what happened after he got kicked out of the Garden and where did the people come from?

He said Cain found the Nubians. He went on to say, "that's where faith comes into play." I was chastised for my eye roll.

I left the church unconfirmed. That was in 1965, when I was 15.

Logic

I was born an atheist, they forced me to be a Christian, I asked a lot of questions, that the answers in their great majority, "It is a mystery of God, it is a sin to question", I am stubborn and I prefer logic! It took me a while to find myself.

Nothing. I was born atheist

The more I learned about religion and science, the more I realized it was all fiction. Simply put, it was education.

I thought about whether or not there was any evidence for the existence of a god and I thought about whether the concept made any sense.

Logic!

Born that way (as we all are) and no one ever changed my mind.

I moved out of my mother's house, no church around (or I did not knew where it was), so I stopped receiving the emotional feedback from religion, so slowly the rational side took over and I could start thinking straight.
Was not exactly a turn, was more like a sustained fight between rational and emotional until the first day I could say that I did not believe...

There wasn't a specific event. I was raised a Catholic and went through the whole process - Catechism, Alter Boy, Confirmation and all that crap. Then after leaving the service nearly 30 years ago I started hitch hiking around the country. While doing that I made some observations that didn't tell me that "God" wasn't real but rather that we're here because we are and die because we do and our relatives don't watch over us after they pass away. Before I knew it, I was more aligned with being a non-theist than I was a Catholic. But it was never anything that I was really thinking about or paid much attention to.

I asked the counselor at a bible camp “how do we know there is god”, when I was 8. The response was “ you just know”
I found that woefully inadequate and my doubt only grew from there. Left the church at 13 and became agnostic, evolved to atheist in early 20’s.

Simple, I learned to ask questions.

I found out there was no Santa Claus.

In 6th grade I questioned a priest regarding eating meat on friday being a mortal sin. I asked him what is the job of the church? He didn't know what I was getting at, so I said isn't it the job of the church to get us to heaven? He agreed. So why is the church making up rules that will send us to hell? "How dare you" was his response. I've been an atheist ever since. And happily so.

I feel like the doubt was always there, and by early teens I was very confident I was right...
I didn't understand how Santa could fit down everyone's chimneys, how he had time to hit every home in the world, and how he could carry so many presents. When I learned he was bogus it just made so much more sense. A few years later I developed a lot of the same practicality type questions about gods until one day it hit me, maybe they're BS too?!?! So I started digging. Very shortly after that I doubted gods were real. And certainly didn't believe the christian version. From then on I sought answers to my questions in the sciences. Go science!

Why Something has to Happen?

I used my brain...was that easy!

Religion!

I read the bible.

Logic slowly took over the intellectual hoops I saw to justify wishful thinking (There's an omniscient being who knows all and cares about all of us... Except some people who suffer through horrific events as part of some grand plan) :/