Ariella Käslin is a Swiss former artistic gymnast. She won all five gold medals at the 2007 Swiss National Championships, and has represented Switzerland at the World Championships in 2007, 2006 and 2005, and was a medalist on the World Cup circuit. Käslin represented Switzerland at the 2008 Olympics, where she placed 18th in the individual all-around final and 5th in the vault event final.

The 40th World Artistic Gymnastics Championships were held at the Hanns-Martin-Schleyer-Halle in Stuttgart, Germany, from 1 to 9 September 2007.