Serena Williams wrote an open letter to her mother and it's utterly kickarse.

Tennis champion Serena Williams – and new mum to Alexis Olympia Ohanian Jr., born two weeks ago – has penned a letter to her own mother thanking her for her strength and love and grace in raising five (FIVE) daughters in a world seemingly pitted against them.

The letter was posted, fittingly, to Reddit, of which Williams’ fiance Alexis Ohanian is co-founder.

In it, Williams reveals the struggles she’s faced living within a “badass” body that is muscular and strong and powerful but which has also been hatefully labelled “masculine” and “steroid-built”.

She thanks her mother, Oracene Price, for setting an example that she could look up to in a world deprived of real examples of real women in all their forms.

“[My daughter] has my arms and legs! My exact same strong, muscular, powerful, sensational arms and body. But I don’t know how I will react if she has to go through what I’ve gone through since I was a 15 year old, and even to this day,” Williams wrote.

“I’ve been called man because I appeared outwardly strong. It has been said that that I use drugs (No, I have always had far too much integrity to behave dishonestly in order to gain an advantage). It has been said I don’t belong in women’s sport – that I belong in men’s – because I look stronger than many other women do. (No, I just work hard and I was born with this badass body and proud of it).

“But mum, I’m not sure how you did not go off on every single reporter, person, announcer and quite frankly, hater, who was too ignorant to understand the power of a black woman.”

My Mom

A post shared by Serena Williams (@serenawilliams) on Jun 10, 2017 at 6:10am PDT

Williams goes onto tell her mother – “one of the strongest women I know” – that she is proud of what she and her sisters – including fellow tennis champion Venus Williams – together with their mother have shown the world.

“Thank you for being the role model I needed to endure all the hardships that I now regard as a challenges – ones that I enjoy. I hope to teach my baby Alexis Olympia the same, and have the same fortitude you have had,” Williams wrote.

Serena Williams schools us in how not to apologise for your work. Post continues below.

Oracene’s job is not yet done, however. With Williams asking her mother for help raising little Alexis.

“Promise me, Mom, that you will continue to help. I’m not sure if I am as meek and strong as you are yet. I hope to get there one day.”

Alexis, we hope the world is kinder to you, than it has been to your mum, and, likely, her mum before that.

You can read Serena Williams’ full letter, here.