'King of Judah' in the Bible

“Say to Rehoboam son of Solomon, king of Judah, to the whole house of Judah and Benjamin, and to the rest of the people,

If these people regularly go to offer sacrifices in the Lord’s temple in Jerusalem, the heart of these people will return to their lord, Rehoboam king of Judah. They will murder me and go back to the king of Judah.”

In the twentieth year of Israel’s King Jeroboam, Asa became king of Judah

However, in the third year, Jehoshaphat king of Judah went to visit the king of Israel.

Now the king of Israel and Jehoshaphat king of Judah, clothed in royal attire, were each sitting on his own throne. They were on the threshing floor at the entrance to Samaria’s gate, and all the prophets were prophesying in front of them.