Ahithophel in the Bible

One of David's counsellors

2 Samuel 15:12 And Absalom sent for Ahithophel the Gilonite, David's counseller, from his city, even from Giloh, while he offered sacrifices. And the conspiracy was strong; for the people increased continually with Absalom.
1 Chronicles 27:33 And Ahithophel was the king's counseller: and Hushai the Archite was the king's companion:

⇒Bible Encyclopedia for AHITHOPHEL.

Joins Absalom

2 Samuel 15:31 And one told David, saying, Ahithophel is among the conspirators with Absalom. And David said, O LORD, I pray thee, turn the counsel of Ahithophel into foolishness.
2 Samuel 15:34 But if thou return to the city, and say unto Absalom, I will be thy servant, O king; as I have been thy father's servant hitherto, so will I now also be thy servant: then mayest thou for me defeat the counsel of Ahithophel.
2 Samuel 16:15 And Absalom, and all the people the men of Israel, came to Jerusalem, and Ahithophel with him.
2 Samuel 16:20-23 Then said Absalom to Ahithophel, Give counsel among you what we shall do. 21 And Ahithophel said unto Absalom, Go in unto thy father's concubines, which he hath left to keep the house; and all Israel shall hear that thou art abhorred of thy father: then shall the hands of all that are with thee be strong. 22 So they spread Absalom a tent upon the top of the house; and Absalom went in unto his father's concubines in the sight of all Israel. 23 And the counsel of Ahithophel, which he counselled in those days, was as if a man had inquired at the oracle of God: so was all the counsel of Ahithophel both with David and with Absalom.
2 Samuel 17:1-23 Moreover Ahithophel said unto Absalom, Let me now choose out twelve thousand men, and I will arise and pursue after David this night: 2 And I will come upon him while he is weary and weak handed, and will make him afraid: and all the people that are with him shall flee; and I will smite the king only: 3 And I will bring back all the people unto thee: the man whom thou seekest is as if all returned: so all the people shall be in peace. 4 And the saying pleased Absalom well, and all the elders of Israel. ...

Probably referred to by David in

Psalm 55:12-14 For it was not an enemy that reproached me; then I could have borne it: neither was it he that hated me that did magnify himself against me; then I would have hid myself from him: 13 But it was thou, a man mine equal, my guide, and mine acquaintance. 14 We took sweet counsel together, and walked unto the house of God in company.

Suicide of

2 Samuel 17:1-14 Moreover Ahithophel said unto Absalom, Let me now choose out twelve thousand men, and I will arise and pursue after David this night: 2 And I will come upon him while he is weary and weak handed, and will make him afraid: and all the people that are with him shall flee; and I will smite the king only: 3 And I will bring back all the people unto thee: the man whom thou seekest is as if all returned: so all the people shall be in peace. 4 And the saying pleased Absalom well, and all the elders of Israel. ...
2 Samuel 17:23 And when Ahithophel saw that his counsel was not followed, he saddled his ass, and arose, and gat him home to his house, to his city, and put his household in order, and hanged himself, and died, and was buried in the sepulchre of his father.