A brother of Goliath the Gittite. According to 1 Chronicles 20:5, Elhanan killed Lahmi. But 2 Samuel 21:19 says that Elhanan killed Goliath rather than his brother Lahmi. Most interpreters accept the 1 Chronicles passage as the correct reading. They consider the 2 Samuel text to be a textual corruption.
Lahmi
From Tyndale Bible Dictionary, adapted by Mission Mutual. CC BY-SA 4.0.