Mo. Rev. Stat. § 26.015
Terms of office.
26.015. Terms of office. — The governor and lieutenant governor shall hold their offices for a term of four years beginning at 12:00 noon on the second Monday in January next after their election and until their successors are elected and qualified.
(L. 1959 H.B. 121, A.L. 1979 H.B. 136)