Arheilgen is a district in the north of the city of Darmstadt in Hesse, Germany, incorporated in 1937.

The place name in its old spelling "Araheiligon" is mentioned for the first time in an undated interest register of Seligenstadt Abbey, which an unknown scribe probably added to a 9th-century gospel book of the monastery around the year 1000.

The surviving residents fled behind the supposedly safe walls of nearby Darmstadt, where many of them died of the plague.

The coat of arms of the town developed from the court seal, the oldest surviving impression of which dates from 1636.

South of Arheilgen is the site of the world's oldest pharmaceutical and chemical company, Merck KGaA.