Bornhagen is a municipality in the district of Eichsfeld in Thuringia, Germany, located at the foot of the ruins of Hanstein Castle.

Hanstein Castle was mentioned for the first time in official documents in the 9th century in Corvey Monastery, and is considered one of the largest castle ruins in central Germany.

During the Thirty Years' War, it was partly destroyed by Swedish troops, after which it was no longer inhabited on a regular basis.

Reconstruction work was begun on the castle in 1985 with the support of the local heritage society.

The three-wing altar from the former castle chapel can be viewed in the Catholic Church in Rimbach.