There is no definitive data available on Europe’s population during the 17th Century.  Different countries and regions had different methods for counting populations, and the question of whether and how to include Russia and Turkey, the latter then the seat of the Ottoman Empire, complicates efforts at providing a solid accounting.  That said, most sources conclude that Europe’s population during the 1600s peaked at about 78 million during the middle of the century, when it leveled off after a period of increase following the end of the periods of plague that had earlier ravaged the continent’s population. 

The main event that affected Europe’s population during the 1600s was the Thirty Years War, lasting from 1618 to 1648.  Combined with the continued effects from the spread of the plague and famine resulting from war and disease, the Thirty Years War cost potentially tens of millions of lives among the combatants fighting on each side of the Roman Catholic-Protestant divide.  As with data on the continent’s population, data on casualties associated with the war is imprecise.  Estimates of the effects of the war on size of population, however, range as high as 40 percent for Germany and similarly high numbers for other regions.