Matthias Flacius Illyricus or Francovich was a Lutheran reformer from Istria, present-day Croatia. He was notable as a theologian, sometimes dissenting strongly with his fellow Lutherans, and as a scholar for his editorial work on the Magdeburg Centuries.

The Magdeburg Centuries is an ecclesiastical history, divided into thirteen centuries, covering thirteen hundred years, ending in 1298; it was first published from 1559 to 1574. It was compiled by several Lutheran scholars in Magdeburg, known as the Centuriators of Magdeburg. The chief of the Centuriators was Matthias Flacius. Lutheran theologian Werner Elert argued that due to its revolutionary critical method of presenting history, it is the basis of all modern church history. It is said that Baronius undertook his Annales Ecclesiastici purely to oppose the Magdeburg Centuriators.