It was Rio 85, without a doubt.. 250,000 two nights each. Hyde Park 76 is probably second place (somewhere between 150 and 200 thousand), but we'll never know for sure because it was a free show.
Feel free to check out the top 10 page on my website for the other big ones.
wasn't largest queen audience at morumbi stadium in brazil? 131 000 people. don't count rock in rio because that was festival with a lot of bands and brazil '81 was all queen audience (unofficially knebworth park was bigger)