Third Creek is a stream in Gasconade and Osage counties of central Missouri. It is a tributary of the Gasconade River.
The stream headwaters are in Gasconade County at 38°21′47″N 91°29′33″W / 38.36306°N 91.49250°W and the confluence with the Gasconade is in Osage County at 38°25′54″N 91°40′02″W / 38.43167°N 91.66722°WCoordinates: 38°25′54″N 91°40′02″W / 38.43167°N 91.66722°W. The stream source is just west of Missouri Route 19 north of Owensville. The stream flows northwest past Old Woollam and, after passing under Missouri Routes P and A, it gains the flow of its southern tributary Crider Creek, and enters Osage County about 1.5 mile before it joins the Gasconade at Cooper Hill.