Marcus Rashford says society is "more divided than ever" in a powerful anti-racism message sparked by the death of George Floyd in Minneapolis.
Floyd died last Monday after a white police officer held him down by pressing a knee into his neck and sports stars have joined in the widespread condemnation.
Manchester United and England forward Rashford said: "I know you guys haven't heard from me in a few days. I've been trying to process what is going on in the world.
"I still struggle to find the words to describe the atrocity of some videos I've seen on Internet. Racism needs to be met with actions, not silence. Please be actively participating, engaging and encouraging others to spread awareness.
"It is our responsibilities to speak out against injustice. Don't be silent. I stand #BlackLivesMatters."
Williams driver George Russell added on the same social media platform: "Now more than ever, we need peace and equality in this world.
"It's time we all stand together and kick racism out of our societies for good. Use your voice, spread awareness as far as you can. We're all responsible for ending the injustice."
Former England captain David Beckham posted on Instagram: "My heart goes out to George's family and I stand in solidarity with the black community and millions of others across the world who are outraged by these events. Its heartbreaking to see that in 2020 this is still happening."
NBA side the Washington Wizards released a joint statement on Twitter, criticising the US Government.
It read: "We will no longer tolerate the assassination of people of colour in this country.
"We will no longer accept the abuse of power from law enforcement.
"We will no longer accept ineffective Government leaders who are tone-deaf, lack compassion or respect for communities of colour.
"We will no longer shut up and dribble."
Former West Ham and Newcastle goalkeeper Shaka Hislop lives in Boston and joined a protest march over the weekend.
The 51-year-old is honorary president of Show Racism The Red Card.
"This is a political issue to be confronted, not a political football to be passed around. And the history of it has to be recognised and respected if it is to be dealt with effectively," he said.
"This is also an issue for every single one of us. To have those uncomfortable discussions with our kids and with each other.
"Being grateful for all that we've been blessed with is not enough, that is not our highest calling. Those conversations aren't easy, nor should they be.
"The riots will end. As will the pandemic and its restrictions. The "normal" that we have enjoyed or endured can be no more. We all have a place in shaping what that new normal looks like, let's all play our parts."
Liverpool's players have also sent their own message and paid tribute.
The squad were pictured taking a knee around the centre circle at Anfield with several stars tweeting the image with the words "Unity is strength".
Joe Gomez, Trent Alexander-Arnold, Jordan Henderson, Fabinho, Adrian, Virgil Van Dijk, James Milner and Dejan Lovren all tweeted the message.
