The post has amassed more than 2.1 million likes and easily become her most-liked ever.
Meanwhile, Lady Gaga shared a lengthy statement via Twitter, explaining that she was "afraid to incite further anger" but that it is "the emotion that's justified".
"I do not wish to contribute to more violence, I wish to contribute to a solution. I am as outraged by the death of George Floyd as I have been by the deaths of exponentially too many black lives over hundreds of years that have been taken from us in this country as a result of systemic racism and the corrupt systems that support it.
"The voices of the black community have been silenced for too long and that silence has proven deadly time and time again. And no matter what they do to protest, they are still met with no compassion by the leaders that are meant to protect them.
"Every day people in America are racist, that's a fact. Right now is a critical time for the black community to be supported by all other communities so we can put a stop to something that is intrinsically wrong by the grace of God or whatever creator you do or do not believe in.
"We have known for a long time that President Trump has failed. He holds the most powerful office in the world, yet offers nothing but ignorance and prejudice while black lives continue to be taken.
"We have known he is a fool, and a racist, since he took office. He is fuelling a system that is already rooted in racism, and racist activity, and we can all see what is happening.
"It's time for a change. I urge people to speak gently to each other, speak with passion, inspiration, and impress the importance of this issue until the systems that keep us sick die, instead of people we love."
Singer Billie Eilish, 18, also joined the chorus, admitting her response was slow off the mark as she'd been trying to "figure out how to address (this situation) delicately" with her "enormous platform" before slamming the "All Lives Matter" movement.
"If I hear one more person say "aLL liVeS maTteR" one more f**king time I'm gonna lose my f**king mind," she wrote.
"Will you shut the f**k up? … This is not about you. Stop making everything about you. You are not in need. You are not in danger.
" ... If all lives matter, why are black people being killed for just being black? Why are immigrants persecuted? Why are white people given opportunities that people of other races aren't? Do you know why? White. F**king. Privilege."
Beyonce also used Instagram to share her emotional reaction, posting a video demanding "justice for George Floyd".
"We need justice for George Floyd. We all witnessed his murder in broad daylight. We're broken and we're disgusted. We cannot normalise this pain," Beyoncé said in the video posted Saturday.
"I'm not only speaking to people of colour; if you're white, black, brown or anything in-between, I'm sure you feel hopeless by the racism going on in America right now. No more senseless killing of human beings, no more seeing people of colour as less than human. We can no longer look away. George is all of our family in humanity. He's our family because he's a fellow American."
It comes as pop star Halsey revealed she was shot at twice by rubber bullets as she joined the frontline of the protests alongside other celebrities including Emily Ratajkowski and Paris Jackson in Los Angeles over the weekend.
Ratajkowski also took to Twitter to share footage from the frontline and criticise the coverage of the protest.
"The media coverage of the #LosAngelesProtest are (sic) complete bulls**t. The police are MILITARISED and civilians have no weapons. These are not violent protests but they become violent when an actual ARMY is deployed. RIOTS ARE THE LANGUAGE OF THE UNHEARD. Try listening!" she wrote.
Paris Jackson, daughter of the late King of Pop, Michael Jackson, also took to Instagram to post a picture of herself among protesters and condemn the outbreaks of violence.
"Today started out so beautifully, seeing people come together with peace and harmony in their hearts. it broke my heart to see it all go up in flames," the 22-year-old wrote.
"Violence is not the answer. How do we expect to bring our world up to a happier and higher and healthier way of living if we're stooping as low as those that committed the crimes we're protesting? Peaceful protest only!"
