The Duke of Sussex told voters to 'reject hate speech, misinformation and online negativity' while the Duchess called the presidential race the 'most important election of our lifetime' as the couple urged Americans to use their right to vote.
Speaking in a Time 100 video message, apparently filmed from the couple's California home, Harry admitted he was not eligible to vote in the November 3 election - adding that he had never voted in the UK either where convention dictates that royals should keep well clear of politics.
But while Harry and Meghan did not endorse a candidate, their intervention sparked criticism from viewers who said it was none of their business.
'Why's a UK prince and his wife getting involved in a U.S. election? What business is it of his? Didn't we fight a war to end interference from the British Monarchy?,' asked one.
Another said it was 'obvious' that the royal couple were supporting Joe Biden, given Meghan's criticisms of Donald Trump before she became a royal - saying their intervention was 'unacceptable for royal family members'.