Okla. Stat. tit. 43 § 101
The district court may grant a divorce for any of the following causes:
First. Abandonment for one (1) year.
Second. Adultery.
Third. Impotency.
Fourth. When the wife at the time of her marriage was pregnant by another than her husband.
Fifth. Extreme cruelty.
Sixth. Fraudulent contract.
Seventh. Incompatibility. Provided, however, where the interest of a child under eighteen (18) years of age is involved, the adult parties shall attend an educational program concerning the impact of divorce on children as provided in subsection B of Section 107.2 of this title.
Eighth. Habitual drunkenness.
Ninth. Gross neglect of duty.
Tenth. Imprisonment of the other party in a state or federal penal institution under sentence thereto for the commission of a felony at the time the petition is filed.
Eleventh. The procurement of a final divorce decree without this state by a husband or wife which does not in this state release the other party from the obligations of the marriage.
Twelfth. Insanity for a period of five (5) years, the insane person having been an inmate of a state institution for the insane in the State of Oklahoma, or inmate of a state institution for the insane in some other state for such period, or of a private sanitarium, and affected with a type of insanity with a poor prognosis for recovery; provided, that no divorce shall be granted because of insanity until after a thorough examination of such insane person by three physicians, one of whom shall be a superintendent of the hospital or sanitarium for the insane in which the insane defendant is confined, and the other two to be appointed by the court before whom the action is pending, and any two of such physicians shall agree that such insane person, at the time the petition in the divorce action is filed, has a poor prognosis for recovery; provided, further, however, that no divorce shall be granted on this ground to any person whose husband or wife is an inmate of a state institution in any other than the State of Oklahoma, unless the person applying for such divorce shall have been a resident of the State of Oklahoma for at least five (5) years prior to the commencement of an action; and provided further, that a decree granted on this ground shall not relieve the successful party from contributing to the support and maintenance of the defendant.
The court shall appoint a guardian ad litem to represent the insane defendant, which appointment shall be made at least ten (10) days before any decree is entered.
Okla. Stat. tit. 43, § 101