The Nahr al-Kalb (Arabic: نهر الكلب, meaning Dog River) is a river in Lebanon. It runs for 31 km (19 mi) from a spring in Jeita near the Jeita Grotto to the Mediterranean Sea.

The Nahr al-Kalb is the ancient Lycus River. The river mouth is renowned for its Commemorative stelae of Nahr el-Kalb, featuring inscriptions from various civilizations. Past generals and conquerors have traditionally built monuments at the mouth of the Nahr al-Kalb, known as the Commemorative stelae of Nahr el-Kalb. The notable inscriptions are of: Assyrian, Babylonian, Roman, Crusader, Ottoman, and modern era.

The entire site of the Nahr el-Kelb valley with the archaeological sites it conceals is classified on the indicative list of UNESCO world heritage.

The river originates at a low altitude from a source that originates from the Jeita Grotto.

As of February 2025, the site remains a focus of historical research and preservation. In November 2023, digital documentation of the cuneiform inscriptions was carried out to support their preservation and study.

33°57′N 35°36′E / 33.950°N 35.600°E / 33.950; 35.600