What was Roger Federer's highest career singles ranking?

Roger Federer's highest career singles ranking was World No. 1. He first reached the top of the ATP rankings on February 2, 2004, becoming the 23rd man to hold the position since computerized rankings began.

Federer spent 310 weeks ranked No. 1, including a record 237 consecutive weeks from 2004 to 2008. His first period at the top followed a breakthrough 2003 season, when he won Wimbledon and the year-end Masters Cup.

Federer returned to No. 1 several times during his career. His final return came in February 2018, when he became the oldest player ever to occupy the top spot at age 36. He held the ranking for 20 weeks during that final reign.

A common mix-up is confusing his year-end ranking with his highest ranking. Federer finished several seasons as No. 1, but his career-high was the same position: the very top of the ATP list.