Liverpool players took a knee around the centre circle at Anfield in a message of support following the death in police custody of African-American George Floyd in Minneapolis.
The picture, featuring 29 Reds players, was posted with the caption “Unity is strength. #BlackLivesMatter”.
Manchester United players Paul Pogba and Marcus Rashford added their voices to worldwide protests against racism.
Protests have been held after Floyd, an unarmed black man, died on 25 May after being restrained by white Minneapolis police officer Derek Chauvin, who kneeled on his neck for almost nine minutes to pin him down.
Chauvin has since been charged with his murder and sacked.