Former PGA champion
Kaymer got up-and-down from a bunker on the par-5 ninth hole to end his round with four straight birdies.
Along with tying the course record on the Stadium Course at the TPC Sawgrass, he broke the nine-hole record with a 29.
It gave the 29-year-old German a two-shot lead over Russell Henley on a day of low scoring.
Kaymer became the fourth player to shoot 63 at the TPC Sawgrass. The others were Fred Couples (1992), Greg Norman (1994) and Roberto Castro (2013).