First: Tseng entered Sunday's final round with a 4-stroke lead over Katherine Hull. Tseng wasn't at her best, shooting 73, but that was good enough to beat Hull by one stroke.
So at age 21 years, 6 months and 9 days, Yani Tseng is now a three-time major champion. And that's where Sarazen comes in. Sarazen was 21 years, 7 months and 2 days old when he won the 1923 PGA Championship, which was his third major. And Tseng has now bettered that.
So now that Tseng has bettered Sarazen in winning No. 3, is she the youngest golfer - male or female - to win three majors? Technically, no, she isn't.
Young Tom Morris won his first British Open in 1868 when he was 17, and then he won the next two. So Tommy Jr. was only 19 at the time of his third major. Of course, professional tournament golf barely existed at that time, and there were no more 20 golfers entered in any of Morris' first three Open wins. The concept of "majors" was far off in the future. This is why many golf records distinguish between pre-1900 and post-1900 eras.
There's also Patty Berg. Berg is the LPGA Tour's recordholder with 15 wins in major championships. She won her first at age 19 at the 1937 Titleholders Championship, and won the next two Titleholders, as well. The Titleholders came into existence in 1937, ceased from 1967-71, returned in 1972, then disappeared for good. It is counted as a major by the LPGA Tour, and wins in the Titleholders are recognized as official LPGA Tour victories. However, Berg's 1937 win, at age 19, does not show up in the LPGA's official records under youngest winners of majors; the Tour apparently does not recognize those ancient Titleholders in this regard. At any rate, given the difference in eras and in quality of fields, Berg's feat doesn't compare at all to Tseng's.
Here's a little perspective on Tseng's accomplishment: She now has as many majors at age 21 as Nancy Lopez won in her entire career. Tseng has now won the same number of majors as Carol Mann, Beth Daniel, Judy Rankin, Jane Blalock and Rosie Jones combined. One more than Dottie Pepper, Lorena Ochoa or JoAnne Carner.
How old were some other prominent golfers at the time of their third major? Here you go:
Bobby Jones, 23
Jack Nicklaus, 23
Tiger Woods, 24
Mickey Wright, 24
Annika Sorenstam, 30
Ben Hogan, 36