There are at least two people named Zedekiah in the Bible. One was king of Judah and the other was a false prophet.
Zedekiah - the false prophet - advised King Ahab of Israel to attack the Syrian army at Ramoth Gilead (1 Kings 22:11). This Zedekiah, who was the son of Chenaanah, made himself horns of iron and said, "The Lord says, 'With these you shall gore Aram until you have destroyed them.'"
Ahab's other false prophets all said the same thing. When Micaiah, a true prophet of God, was called on, he gave a disasterous prediction to the outcome of the battle for King Ahab and Israel. When Zedekiah heard this he slapped Micaiah on the cheek, saying, "Has the Spirit of the Lord, then, left me to speak with you?" (1 Kings 22:24). The battle, in which King Ahab was mortaly wounded, ended up as Micaiah predicted. The fate of Zedekiah is not written in the Bible after his false prophecy.
The other Zedekiah - the king of Judah - was a son of King Josiah and Hamutal, and uncle to King Jehoiachin. He was appointed King of Judah, after King Jehoiachin was exiled by King Nebuchadnezzar of Babylon. He reigned eleven years, but it was an evil reign (596-586 BC). The idea of a king appointed by a foreign ruler was not accepted by the people who continued to regard Jehoiachin as their legitimate king (Jeremiah 37:1).
King Zedekiah refused to accept the counsel of Jeremiah the prophet, who gave him messages of the Lord. He rebelled against King Nebuchadnezzar, even though he had taken an oath of loyality. (2 Chronicles 36:12-13). King Nebuchadnezzar then laid siege to Jerusalem in the ninth year of the reign of King Zedekiah, and continued to the eleventh year. The food had run out, and Zedekiah tried to escape, but was captured in the plains of Jericho.
He was then taken to Riblah, where he was tried and sentenced before the King of Babylon. He was forced to watch as his sons were killed before his eyes, then his eyes were put out and he was taken to Babylon (2 Kings 25:6-7). General Nebuzaradan of Babylon then burned down the Temple and the palace, and tore down the walls of Jerusalem. The story of Zedekiah is found in 2 Kings 24:17-20, 25, and 2 Chronicles 36:11-13. The name Zedekiah means "Yah is my righteousness."
Next person in the Bible: Zephaniah