Wassy () is a commune in the Haute-Marne department in north-eastern France. Wassy has been twinned with the German town of Eppingen in north-west Baden-Württemberg since 1967.
On 1 March 1562, a faction of armed soldiers under Francis, Duke of Guise attacked and killed worshippers at a Huguenot service, called the Massacre of Wassy, which marked the start of the First War of Religion in France.
The river Blaise flows through the commune.