The most people washing their hands in multiple locations was 740,870 in an event organised by the Pan American Health Organization, Region of the Americas, at multiple venues in Argentina, Mexico and Peru on 14 October 2011.
The record was set on Global Handwashing Day 2011 and was done to promote how washing your hands helps to stop the spread of germs and prevent persons from getting sick. Most of the participants were children and their teachers and in some locations even the governors of states participated. The participation breakout, determined by country was 604,246 participants in Peru, 134,790 participants in Mexico and 1,834 participants in Argentina.
Comments below may relate to previous holders of this record.