Roger Federer's 2018 tennis season officially began on 30 December 2017, with the start of the Hopman Cup, and ended on 17 November 2018, with a loss in the semifinals of the ATP Finals. He finished the year ranked No. 3 in the ATP Rankings. This season saw Federer improving his career best start to a season at 17–0 (21–0 if including victories at the Hopman Cup). Federer won his twentieth major at the Australian Open and extended his then-record of weeks at World No. 1 to 310 weeks in this season.