Karin Nathalie Ruckstuhl (born 2 November 1980 in Baden, Switzerland) is a former Dutch heptathlete.

She came close to the podium at the 2004 IAAF World Indoor Championships, finishing fourth, and took part in her first Olympics at the 2004 Athens Games, where she was 16th in the final rankings with a national record of 6108 points.

However, she did not manage to finish the heptathlon at that year's major competition – the 2007 World Championships in Athletics.

Her time out from the sport was extended even further after she injured her Achilles tendon in February 2010.

Following such serious injuries and some two and a half years away from top level competition, she decided to stop competing in multi-sport events and focused her efforts on just long jumping.