Burg Horkheim, Medieval castle in Heilbronn, Germany.

Burg Horkheim is a water castle on the western edge of Horkheim, now part of Heilbronn. Its oldest parts are a 16-metre, four-storey stone house and remains of the five-sided perimeter wall with two corner towers, once ringed by a 10-metre moat. The first upper floor keeps Gothic vine paintings and traces of painted coats of arms; the second has Hebrew characters and remains of Renaissance ornament. A two-storey residential building with decorative timber framing was added in 1550 by Volmar Lemlin, whose coat of arms and that of his wife, born von Rinderbach, stand beside the date on a corner post.

Burg Horkheim was first mentioned in 1344 and belonged to Eberhard II of Württemberg, who sold it in 1389 to the Teutonic Order's Heilbronn commandery. In 1459 the order passed it to the Heilbronn patrician family Lemlin, who placed it under the overlordship of the Electorate of the Palatinate in 1461. Volmar Lemlin and his wife Agnes vom Bach endowed the castle chapel's benefice on 11 May 1469.

The synagogue inside the residential tower was first mentioned in 1725 and remained in use into the 19th century. A fresco found during restoration shows a Torah ark and a German inscription written in Hebrew letters. The lane now called Schlossgasse was once known as Judengasse.

The castle lies west of Horkheim's old village centre, in low ground near the Neckar, so it is almost invisible from the village itself; the 16-metre residential tower is seen from the river and from the south-west. The former moat is partly filled in, and the surviving dry section is used as a garden. The site is now in private ownership, so the grounds and buildings should be viewed from outside.

In the 1740s, around 90 people from 17 Jewish families lived within the castle walls without paying the usual protection fees. This arrangement made the castle a special refuge for the Jewish population at that time.