Nina Kathy Rillstone (born April 15, 1975 in Brentwood, Essex) is a New Zealand long-distance and marathon runner.
She is a national champion in both middle and long distance running, and a national record holder for the half-marathon.
She set her personal best for the Half Marathon of 1:13:03 at the 2005 IAAF World Half Marathon Championships in Edmonton, Alberta, Canada.
Her personal best in the marathon came during the Nagano Marathon in 2006, with a time of 2:29:46.
Rillstone set a national record for the marathon at the 2007 IAAF World Championships in Osaka, Japan, with a time of 2:33:58, finishing in thirteenth place.Rillstone represented New Zealand for the 2008 Summer Olympics in Beijing, and competed in the women's marathon.
She ran and finished the race in sixteenth place, with a best possible time of 2:31:16, nearly two minutes short of her personal best set in Nagano.