Her books have sold 173 million copies around the world and been translated into 55 different languages. She's also had them made into two hit films!
As well as working tirelessly on the Harry Potter books - she also works for good causes.
She's helped raise thousands for the charity One Parent Families. And also for Maggie's Centre - which helps cancer sufferers and their families.
Cash for charities
And a few weeks ago JK organised a ball that raised £275,000 for the charity Multiple Sclerosis - Scotland.
Two books she wrote for Comic Relief have raised nearly 5 million pounds in this country alone.
That money will go to help children across the world that aren't as lucky as us.
JK has captivated millions of us with the power of her imagination but she's used Harry's success not only to entertain us - but also to try and make a real difference to people's lives.
That is true magic - and why I'm asking you to vote for JK Rowling as your Greatest Briton!"
Sera, 13, Wales
Tune into CBBC's Newsround all this week to see special Press Pack reports on each of the finalists in our very own greatest Briton series.
There's a different person each day this week and YOU can vote for your favourite.