A double or a look-alike of oneself — often described in folklore or fiction as a counterpart or apparition resembling a person.
彼女は街で自分のドッペルゲンガーを見かけたと言った。
She said she saw her doppelgänger on the street.
その小説では主人公が自分のドッペルゲンガーと対面する場面が印象的だ。
In that novel, the scene where the protagonist meets his doppelgänger is striking.
ドッペルゲンガーは分身や幻影として語られることが多い。
Doppelgängers are often spoken of as doubles or phantoms.