Who was Goliath?
In the Hebrew Bible or Christian Old Testament, Goliath was the Philistine giant who was killed by David.
The giant of Gath, and champion of the Philistine army (1 Samuel 17:4-23 ; 1 Samuel 21:9 ; 1 Samuel 22:10 ; 2 Samuel 21:19 ; 1 Chronicles 20:5 ). He defied the armies of Israel, challenging anyone to meet him in single combat while the two armies faced each other at Ephesdammim.
He was slain by the youthful David. Goliath was almost certainly not of Philistine blood, but belonged to one of the races of giants, or aboriginal tribes, such as the Anakim, Avvim, Rephaim, etc. The Avvim had lived at Philistia, and most probably the giant was of that race. His size was most extraordinary. If a cubit was about 21 inches, he was over 11 feet in height; if about 18 inches, he was over 9 feet in height.
The enormous weight of his armor would seem to require the larger cubit. This height probably included his full length in armor, helmet and all. In either case he is the largest man known to history. His sword was wielded by David to slay him and afterward carried about in his wanderings, so it could not have been excessively heavy. The story of his encounter with David is graphic, and the boasts of the two champions were perfectly in keeping with single combats in the Orient.
IBSE, (in the public domain) with minor edits.