An exact year is difficult, but it was invented by Dom Perignon at the hautvilliers vineyard between 1668 and 1715. Moet and Chandon named one of their better wines after him.
Champagne was certainly DEVELOPED in central France in the late 17th century, but as I understand it, fizzy wine was first bottled in England, because of our much superior glass-making (and hence bottle-making) techniques, so it might be as true to claim that we invented champagne here....