Clarke Johnstone (born 26 April 1987) is a New Zealand equestrian, competing in eventing.

[2] At the 2010 FEI World Equestrian Games in Lexington, Kentucky, he won the bronze medal with the eventing team alongside Andrew Nicholson, Mark Todd, and Caroline Powell.

At the 2011 CHIO Aachen in Germany, he won the silver medal in the team event alongside Nicholson, Powell, and Jonathan Paget.

Johnstone missed out on selection for the 2012 Summer Olympics; his main horse — Orient Express — was injured and he thus was not chosen.

At the 2016 Summer Olympics, he finished sixth in the individual and fourth in the team event.