According to an article at the USCF, Viswanathan Anand is the oldest player to win the World Championship since Mikhail Botvinnik regained the title in 1961 from Mikhail Tal. I take great comfort in that :-)
Some other interesting "oldest in chess" (courtesy of Bill Wall's Oldest in Chess)
- The oldest world chess champion was Wilhelm (William) Steinitz, who won a world championship match from Chigorin at the age of 56. He was world champion until he lost it in a match with Lasker in 1894 at the age of 58 years, 10 days.
- The oldest qualifier for the World Chess Championship was Vassily Smyslov (1921- ), who became a Candidate by taking 2nd place in the 1982 Las Palmas Interzonal at the age of 61.
- The oldest player to become a master was Oscar Shapiro. He became a USCF master at the age of 74.
- The oldest person to win a national chess championship was Edith Price (1872-1956), who won the British Ladies Championship in 1948 at the age of 76.
- The oldest person to win a state chess championship was Harlow Daly (1883-1979), who won the chess championship of Maine in 1969 at the age of 85.
- Encrico Paoli is the oldest active chess player in the world as of 2004. He is 96.