Affenstein, Castle ruin in Bad Kreuznach, Germany.

Affenstein is a castle ruin located in Bad Kreuznach that sits on elevated terrain with remains of medieval fortification architecture visible throughout the site. Partial walls and foundation structures show the outline of how the original fortress was built and organized.

Affenstein is first documented in 1426 as "Affensteine unter Ringravensteine", a fief of the Rheingrafschaft held in part by Henne von Lonsheim and Johann von Wonsheim. It probably served as an outer bailey of Rheingrafenstein Castle. Its destruction is unrecorded but likely tied to the 1688 destruction of Rheingrafenstein.

The name Affenstein appears only once in the records, in a 1426 document calling it "Affensteine unter Ringravensteine", which places it under the Rheingrafschaft fief. Henne von Lonsheim and Johann von Wonsheim are named there as part-owners. The site is presumed to have been a forward castle (Vorburg) of Rheingrafenstein, guarding the slope above the Nahe.

The site lies at about 230 m above sea level on the steep southwestern drop of the Rheingrafenstein, halfway between the castle and the Nahe. The slope is hard to access and only a few broken-stone wall remains survive, so an inspection is difficult. Sturdy footwear is needed.

Affenstein is documented only once, in 1426, as "Affensteine unter Ringravensteine", when Henne von Lonsheim and Johann von Wonsheim are named as part owners of the castle held as a fief of the Rheingrafschaft. Its destruction is unrecorded but probably linked to that of Rheingrafenstein in 1688.