International Childfree Day is celebrated every year on Aug. 1 to honor those who choose not to have a kid. While raising a child can be an enriching experience for many, hundreds have proved that success is not measured by a kid or the lack of it. 

Started in 1973 by the National Alliance for Optional Parenthood, the International Childfree Day pays tribute to people who make an impact on society, taking advantage of their lifestyle choice.

However, the day was revitalized by author Laura Carroll in 2013. She felt the day should be observed to recognize the amazing childfree people and help promote acceptance of the choice in contemporary times.

So, on this special day, let's learn about a few celebrities who have been vocal about their choice to remain childfree.

1) Oprah Winfrey: The very famous talk show host Oprah has always been vocal about how "having a baby didn't feel right for her." "I don’t think I would have been a good mother for baby children, because I need you to talk to me, and I need you to tell me what’s wrong," the star said on Gwyneth Paltrow's Goop podcast. "I can’t just figure it out. And I was always - I knew this about myself."

2) Renee Zellweger: The actor, who has played a pregnant woman and mother on the screen, said she hasn't thought too much about motherhood. "I’ve never really thought like that about anything in my life, really. I’ve always been kind of open to whatever may be, curious to see what’s next. I’ve never been that deliberate about my life and the things that I would require in order to be happy," Zellweger told US Magazine.

3) Helen Mirren: The great Helen Mirren opted to go childfree though she maintained it was never "an absolute conscious decision." "I was always too engaged in my life as an actress," the star told presenter Peter Travers. "At that time, I couldn't comprehend that you could incorporate a child into that without letting a child down in some way. It was never an absolute conscious decision, it was just, 'Oh, maybe next year, maybe next year,' until really there was no next year." 

4) Ricky Gervais: The actor has often opened up about why she cannot have kids. "I didn’t have a work ethic for such a long time. Imagine if I had a child like me? I didn’t start earning until I was 36. I’m the sort of person who has to check three times that I’ve shut the door, so I’d probably stare at a kid all day to check it was breathing," Gervais told Red Magazine in 2009.

5) Jon Hamm: "The Mad Men" actor is sure he doesn't want any children. In fact, he is certain he would have been a terrible father. "I see my friends who have children and I'm like, 'Dude, how are you even upright, much less here at work at 6 a.m.?" Hamm told US Weekly.

Oprah Winfrey Oprah Winfrey Photo: Getty Images/Ben Gabbe