Madison Keys has long been a strong voice against online abuse, and this month she's taking her efforts worldwide—with the inaugural Kinder Girl World Day, on May 21. 

As girls, women and tennis players know all too well, social media can be a hurtful place. So Keys and the organization Fearlessly Girl are starting Kinder Girl World Day with the purpose of drowning the hatred out with positivity.  

Next Tuesday, participants are encouraged to send kind and supportive messages to girls and women on social media, using the hashtag #KinderGirlWorldDay

"I want to help make social media a better and safe space for everyone where we can all feel uplifted and loved," Keys wrote on Instagram. 

At April's Volvo Car Open, Keys received the Player Who Makes a Difference Award, along with a $10,000 donation to Fearlessly Girl. She also won the tournament.