[2] The two played together in the final two rounds and had separated themselves from the field under clear skies, leading this Open to be remembered as the "Duel in the Sun."
The previous year, Watson was defending champion, but missed the 54-hole cut after an 80 in the third round, while Nicklaus finished in a tie for second.
Watson birdied three of the next four to pull even at two-under for the round, then bogeyed the ninth hole to fall one back at the turn.
Watson missed an eagle putt and tapped in for birdie, but then Nicklaus two-putted for par to go a stroke down with one hole remaining.
Watson's 7-iron approach stopped pin-high and two feet left of the flag, and with Nicklaus in trouble, appeared to seal the victory.
Now needing a seventh birdie of the round to avoid an 18-hole playoff, Watson sank the two-footer for his second straight 65, second Open, and third major title.