The event, which takes place on Monday, marks what would have been the 41st birthday of presenter Caroline Flack. The celebrated TV presenter tragically took her own life earlier this year.
Earlier this year Meghan described herself as “the most trolled person in the entire world in 2019” whilst discussing mental health on a podcast.
Meghan’s endorsement was revealed by the Social Media Kindness Day via its official Twitter account.
The Duchess said: “For so many, social media plays a big part of their daily life.
“We have access to it at the end of our finger tips, so it ought to be a safter and kinder place for all.
“Most people would never make the nasty remarks they do on social media to a person’s face.
“This is because they would be able to see the hurt and upset caused by those words.
“Social media should be a place where people can socialise, network, do business and live ‘their best life’ without fear of negativity.”
In January the Duke and Duchess of Sussex caused a global sensation when they announced their intention to step down as senior members of the Royal Family.
Instead the couple said they would become “financially self-sufficient” and split their time between Britain and North America.
They moved to California, Meghan’s home state, shortly before the coronavirus lockdown came into effect.
Earlier this year Meghan spoke out about online abuse during an appearance on the Teenager Therapy podcast.
She said: “I can speak personally because I’m told that in 2019 I was the most trolled person in the entire world – male or female.
“Now eight months of that I wasn’t even visible. I was on maternity leave or with a baby.
“But what was able to just be manufactured and churned out. It’s almost unsurvivable.”
For mental health assistance Samaritans (116 123) or email [email protected] operates a 24-hour service available every day of the year.