The 2017 Australian Open Men's Singles final was the championship tennis match of the Men's Singles tournament at the 2017 Australian Open. It was contested between Roger Federer and Rafael Nadal, ranked 17th and 9th in the world respectively. It was their record ninth meeting in a Grand Slam final in their rivalry, and their 1st meeting in a Grand Slam final since the 2011 French Open. In a rematch of the 2009 Australian Open final, which Nadal won in 5 sets, Roger Federer won the duel in 5 sets, beating Nadal for the first time in a Grand Slam since the 2007 Wimbledon final. He also trailed Nadal 3 -- 1 in the final set but won 5 games in a row to win the title. This ended a 6-match losing streak against Nadal in Grand Slam events. Having lost all of their previous three encounters, this was the first time Federer defeated Nadal at the Australian Open and also marked Federer's first Grand Slam victory over Nadal outside the grass courts of Wimbledon. Federer extended his record of Grand Slam men's singles titles to 18 exceeding the previous record of 14 held by Pete Sampras.

Based on this passage, who won the australian men's open final? Let's give stream of consciousness first:
The relevant information to answer the above question is: Having lost all of their previous three encounters, this was the first time Federer defeated Nadal at the Australian Open and also marked Federer's first Grand Slam victory over Nadal outside the grass courts of Wimbledon.
So, the final answer is Federer.