Orekhovets or Orechovets is an island with the fortress Oreshek (Nöteborg in Swedish, given the name Shlisselburg/Schlisselburg/Schlüsselburg (also sometimes erroneously spelled as Schlüsselberg, Schlusselberg, Schluesselberg) after its re-conquest by Peter the Great in 1702). The island is situated in Lake Ladoga at the inlet of River Neva, close to Saint_Petersburg, Russia. The fortress was erected sometime in late 13th century or in beginning of 14th century. In Imperial Russia, the fortress was also used as a prison.

The name of the island refers to Nuts in both Swedish, Finnish (Pähkinäsaari/Pähkinälinna) and Russian. The German name Schlüsselburg refers to Peter's perception of the fortress as the "Key to Finland".