What I mean is, a conference or collection of countries' that came together to discuss whatever was relevant at the time? And (not meaning to incite discussion about the current UN's effectiveness) did it work?
There was the League of Nations that was established after WWI at the Paris Peace Conference. It had a ton of members at one point (40+) including major European powers.
It fell apart though; this is due to it not having an armed force, and ontop of that none of the member nations were ever willing to reinforce its policies thus causing it to crumble and become a hindrance rather than positive thing.