Okla. Stat. tit. 57 § 353.1
In all cases where a sentence of imprisonment in the State Penitentiary is imposed, the court, in assessing the term of the confinement, may fix a minimum and a maximum term, both of which shall be within the limits now or hereafter provided by law as the penalty for conviction of the offense. The minimum term may be less than, but shall not be more than, one-third (1/3) of the maximum sentence imposed by the court. Provided, however, that the terms of this section shall not limit or alter the right in trials in which a jury is used for the jury to assess the penalty of confinement and fix a minimum and maximum term of confinement, so long as the maximum confinement be not in excess of the maximum term of confinement provided by law for conviction of the offense.
Okla. Stat. tit. 57, § 353.1