In the early 1900s the Grand Slam meant consecutive victories at the United States Amateur Championship, The Amateur Championship (British Amateur), the US Open and the Open Championship.
Bobby Jones is the only man who has ever achieved a Grand Slam. He did so in 1930.
In modern golf the Grand Slam requires winning all 4 Major Tournaments in a single calendar year.
To date no professional golfer has accomplished the modern Grand Slam. Tiger Woods came close with his 'Tiger Slam' where he held all four Majors at the same time, but not in one calendar year.
Updated: 3-Jun-2021 | Email feedback to this question