Heiningen is located on the southeastern rim of the Oderwald hill range, about 11 kilometres (6.8 mi) south of the district capital Wolfenbüttel.

The municipality is the site of medieval Heiningen Abbey, established about 1000 AD by the Saxon noble House of Billung.

The Rule of St. Augustine was implemented in 1126, while the building of the Sts Peter and Paul monastery church, a Romanesque basilica, began.

After the fierce Hildesheim Stift Feud, Heiningen was occupied by the forces of Duke Henry V of Brunswick and the monastery turned Protestant in 1569.

Restored to the Bishopric of Hildesheim in 1643, the abbey church again was consecrated Catholic, while the population largely retained the Protestant faith.