Wasannin Isthmian jerin gasa ne na motsa jiki da na al'adu da ake gudanarwa duk shekara biyu a tsohuwar Girka a Isthmus na Koranti. Kalmar “Isthmian” tana nufin Isthmus na Koranti, wanda ɗimbin ɗigon ƙasa ce wadda ta haɗa yankin Peloponnese zuwa babban yankin ƙasar Girka. Wasannin na ɗaya daga cikin wasannin Panhellenic guda huɗu na tsohuwar Girka, tare da wasannin Olympics, Pythian, da na Nemean. Wasannin Isthmian sun haɗa da wasannin motsa jiki iri-iri, waɗanda suka haɗa da guje-guje, kokawa, dambe, da tseren karusa, da kuma gasa na kiɗa da waƙoƙi. An gudanar da wasannin ne don girmama allahn Poseidon, wanda aka ɗauke shi majiɓincin Isthmus na Koranti.