Burg Alt-Hohensolms, Medieval castle in Hohenahr, Germany.

Burg Alt-Hohensolms is a medieval fortress situated on the Altenberg hill at approximately 442 meters in elevation. The complex features defensive stone walls and a reconstructed lookout tower added in the 19th century that dominates the site.

Founded in 1321 by the Counts of Solms, the fortress was built to protect their territory from the Landgraves of Hesse. It controlled key trade routes north of Wetzlar and held strategic importance in the region's political landscape.

The castle's name distinguishes it from Burg Hohensolms, built around 1350 on the Ramsberg about two kilometres north after Alt-Hohensolms was destroyed; the older site was later called only Altensolms. The counts' castle also guarded the trade routes that met near the Altenberg, and Wetzlar repeatedly complained about attacks on merchants by Solms castle men.

Only remnants of the wall and ditch systems remain on the Altenberg; the site is freely accessible on foot. The observation tower built in the 19th century by Prince Ferdinand of Solms-Hohensolms-Lich can be climbed for a view. The nearest town is Hohenahr, and Wetzlar lies about 20 km away.

The Counts of Solms got around Emperor Charles IV's ban on rebuilding by constructing a new castle, Hohensolms, about two kilometres north on the Ramsberg around 1350. The old site was later called Altensolms. In the first half of the 19th century, Prince Ferdinand of Solms-Hohensolms-Lich had a lookout tower built, probably from stones of the former castle.