Omenainen (or Ominainen; Swedish: Ominaisholmen) is a state-owned uninhabited island in the municipality of Nagu (now Pargas), Finland, in the central Archipelago Sea.

The size of the island is about seven hectares and its highest point is about 22 meters high.

[3][4] The dead of the parishioners of Rymättylä and Nagu, who the church refused to bury in the blessed land, such as murderers, suicides and other sinners, were once taken to the island.

In folklore, the island has a frightening reputation: it is considered cursed and ghost stories are told about it.

[1][5][6][7] Based on the stories, the author Maila Heikkilä published the youth book Yö kummitussaaressa ("Night on the Ghost Island") in 1986; in the book, the protagonist Janne finds a newspaper story about the ghost island called Omenainen and entices his sister Päivi to spend the night on the island with him.