Gideon was one of the judges of Israel, called by an angel of the LORD to deliver Israel from the Midianites, recorded in Judges 6-8.
Judges 6:12 in the King James Version reads:
And the angel of the LORD appeared unto him, and said unto him, The LORD is with thee, thou mighty man of valour.
The verse appears in Judges 6, in the account of the angel of the LORD appearing to Gideon. Read it in context at Judges 6:12, or the full chapter at Judges 6. Encyclopedia entry: en.wikipedia.org/wiki/Gideon.