Omri was the sixth king of the northern kingdom of Israel. He is remembered for his great wickedness, his establishing of Samaria as his capital city and as being the father of Ahab who married Jezebel the evil daughter of the malevolent King Ethbaal of Sidon.
While politically, the relocation of the capital to the fortified hill of Samaria and the matrimonial alliance with Sidon were masterstrokes and worthy of remembrance, so was Omri's wickedness. He did not humble his heart before God and he instead sinned more than all the kings of Israel before him (and that's saying a lot). Furthermore, he taught his son Ahab (by example) to sin even more than he did.
Omri was a general in the army of King Elah of the northern kingdom of Israel. Elah was assassinated in an attempted coup by another military man Zimri in the capital at Tirza. Zimri was deposed after 7 days of rule and committed suicide. Omri was then made king. Omri reigned 12 years.