The Council of Trent happened after the Protestant Reformation, in response to it. The Protestant Reformation is usually dated as beginning in 1517 with Martin Luther's posting of his 95 Theses concerning the sale of indulgences. The Council of Trent was held over a span of years from 1545 to 1563. It served to reform some abuses that were acknowledged by the Catholic Church. Mostly, though, the Council aimed to assert the full authority of Roman power and doctrine over the Protestant threat So you could say the Council of Trent was a consequence of the Protestant Reformation -- it was not a cause of it.
