Khirbet Mazin, Archaeological site at Dead Sea shore, Israel.

Khirbet Mazin is an archaeological site with ruins of an ancient fortress located on the northwestern shore of the Dead Sea. The remains show a dry dock system that was built to support boat operations on the water.

The older ruins date to the end of the First Temple Period, in the 8th–7th centuries BCE, identified by Israelite pottery found there. During Hasmonean times the fortress was enlarged and a dry dock added. A hoard of about 2,500 bronze coins of Alexander Jannaeus, found on the shore in 2002, dates the port works to his reign.

The name Metzad Kidron means "stronghold by Kidron" in Hebrew, while Khirbet Mazin comes from the nearby Wadi Mazin. The first archaeologists named it after the wadi; it was later also called Qasr el-Rubai and identified with Qasr el-Yahud. The tower housed the workers and royal guests who used the anchorage.

The location is in a remote area by the Dead Sea and is best reached by vehicle or guided tour. Visitors should bring water, sun protection, and sturdy footwear since the ground is uneven and offers little shade.

The dry dock held a ramp used to haul boats out of the water so their hulls could be washed with fresh water to remove salt. Beside it stood a 15-metre jetty where boats loaded and unloaded cargo, and the archaeologist Yizhar Hirschfeld considered the harbour a royal anchorage serving Alexander Jannaeus.