Saudi Arabia is an absolute monarchy that does not tolerate any political opposition, but the formation of the National Assembly Party on the anniversary of the kingdom's founding comes amid a growing state crackdown on dissent and freedom of expression.
"We hereby announce the establishment of the National Assembly Party, which aims to institute democracy as a form of government in the kingdom of Saudi Arabia," the group said in a statement.
The development is unlikely to seriously undermine the authority of the Arab world's most powerful ruling family.
But it poses a fresh challenge to Saudi Arabia's rulers as they grapple with low crude oil prices and gear up to host a G20 summit in November amid the coronavirus pandemic.
There was no immediate reaction from Saudi authorities.