According to Official Guinness Records,
The oldest female to complete a marathon was Gladys Burrill (USA) at the age of 92 years 19 days at the Honolulu Marathon in Honolulu, Hawaii, USA, on 12 December 2010. Burrill completed the race in 9 hr, 53 min, 16 sec.
Burrill was born on 23 November 1918.
For a complete list of 2010 records, please visit 2010 Guinness Records in United States.