Okla. Stat. tit. 11 § 48-101
The governing body of any municipality may provide by ordinance for a retirement fund and system for any or all of its employees and the employees of a duly constituted authority of the municipality which are not otherwise provided for by a pension or retirement system. The governing body may establish said retirement system as delayed compensation in order to encourage continuous and meritorious service on the part of employees and thereby promote public efficiency, and may provide retirement allowances and other benefits for said employees, their surviving spouses, and surviving children. The retirement fund and system may include all municipal employees whether they are engaged in a governmental or nongovernmental function of the municipality or the municipal authority. The retirement fund shall be supported wholly by the municipality or municipal authority or by joint contributions by the municipality or authority and the employee to be benefited.
Okla. Stat. tit. 11, § 48-101