who is the youngest GM in the world?

Check this information:

http://susanpolgar.blogspot.com/2009/10/perus-jorge-cori-became-gm-at-14-years.html

I think Kasparov has been the youngest GM ever or....?

 Karjakin holds the record as youngest GM ever.

Jorge Cori. I read that article on Susan's blog and I looked up his FIDE rating, and it was about 2450. To be a GM you must have reached 2500 at some point, as a requirement.

Maybe his latest tournaments push him over that and they haven't been rated yet. I don't know, but there are innaccuracies in the article, such as saying his sister was a GM (she is not) and is in the top 80 in the world (no). I'm just not trusting this apparently chess-ignorant author.

We'll see.

edit: His sister is a WIM and is 98th in the world among women.

So if you get to 2500 then become a GM what happens if your ratings go back down?  Are you still recognised as a GM or do you get relegated? 

A GM is forever. "It is not necessary to maintain the Elo rating and the criterion is that the person (he or she) must have the ELO rating of 2500 to qualify for the title."

There is a list here dated 2009 10 23.

"1. Sergey Karjakin UKR 12 years, 7 months, 0 days

2. Parimarjan Negi IND 13 years, 4 months, 22 days

3. Magnus Carlsen NOR 13 years, 4 months, 27 days

4. Bu Xiangzhi CHN 13 years, 10 months, 13 days

5. Teimour Radjabov AZE 14 years, 0 months, 14 days

6. Ruslan Ponomariov UKR 14 years, 0 months, 17 days

7. Wesley So PHI 14 years, 1 month, 28 days

8. Etienne Bacrot FRA 14 years, 2 months, 0 days

9. Maxime Vachier-Lagrave FRA 14 years, 4 months

10. Péter Lék� HUN 14 years, 4 months, 22 days

11. Hou Yifan CHN 14 years, 6 months, 16 days

12. Anish Giri NED 14 years, 7 months, 2 days

13. Yuriy Kuzubov UKR 14 years, 7 months, 12 days

14. Dariusz Swiercz POL 14 years, 7 months, 29 days

15. Nguyen Ngoc Truongson VIE 14 years, 10 months

16. Ray Robson USA 14 Years 11 Months 16 days

17. Fabiano Caruana ITA 14 years, 11 months, 20 days

18. Humpy Koneru IND 15 years, 1 month, 27 days

19. Hikaru Nakamura USA 15 years, 2 months, 19 days

20. Pentala Harikrishna IND 15 years, 3 months, 5 days

21. Judit Polgar HUN 15 years, 4 months, 28 days

22. Alejandro Ramirez CRC 15 years, 5 months, 14 days

23. Bobby Fischer USA 15 years, 6 months, 1 day"