I was curious and checked https://en.wikipedia.org/wiki/List_of_largest_peaceful_gatherings_in_history https://en.wikipedia.org/wiki/List_of_largest_peaceful_ga

I was curious and checked https://en.wikipedia.org/wiki/List_of_largest_peaceful_gatherings_in_history https://en.wikipedia.org/wiki/List_of_largest_peaceful_gathe.... It includes all gatherings of people, not just marches or demonstrations. I was impressed by the numbers of some of the top gatherings. The shared record is for two religious events at ~30 million people in India and Iraq.