Csepel-sziget (or Csepel Island) is the largest island of the River Danube in Hungary. It is 48 km long; its width is 6-8 km. Its area comprises 257 km².

It is located south of Budapest; its northern peak is Csepel, District XXI of the capital. Most of the island is available from Budapest by HÉV, the suburban railway (albeit a different one from which takes to the city part Csepel).

Its most notable town is Ráckeve . Among the further towns are Szigetszentmiklós , Szigethalom and Tököl (the latter known for its prison).

It was the first centre of conquering Hungarians, being the lodgement of Árpád's tribe. The name itself originates from Árpád's groom, Csepel.