FamilySearch has digitized 33 microfilm reels of Lancaster County, South Carolina Marriage Licenses, 1911-1950. You can access the microfilms via the FamilySearch catalog here.
To view the microfilms, click on the camera icon to the right of the microfilm description, as in the example below:
These records are not yet part of an indexed collection, so you will need to read through the microfilms just as you would at a library. Happy ancestor hunting!