Who United the Twelve Tribes of Israel? King David

The Twelve Tribes were never fully united under a single ruler; however, King David (c. 1010–970 BCE) achieved the closest approximation:

• Captured Jerusalem (c. 1000 BCE), made it capital.
• Consolidated tribal coalitions into a unified monarchy.
• His son Solomon expanded the kingdom; after Solomon's death, it split into Israel (north) and Judah (south).

Earlier, Saul ruled a loose confederation; later, no single king reunited the divided kingdoms.