The brief is focused on hand hygiene. We have long understood the importance of hand hygiene for the reduction of diarrhoeal diseases, respiratory infections, hospital-acquired infections and during outbreaks like cholera and Ebola. Hand washing with soap or alcohol-based hand rub is an effective COVID-19 prevention measure along with physical distancing and appropriate mask use. Despite the many benefits of hand hygiene, actual practice remains low globally. The COVID-19 pandemic has already led to short-term improvements in hygiene behaviour but it is now critical to translate these improvements into longer-term handwashing habits and policy change so that the immediate threat of COVID-19 is addressed and progress can be made to reduce the burden of other faecal-oral diseases. In this brief, we present 10 key lessons gleaned from the work of the COVID-19 Hygiene Hub. These insights emerged from hundreds of informal conversations that we have had with programme implementers across 60 countries between April and October 2020.