Lang Suan is a district (amphoe) of Chumphon Province with a coastline on the Gulf of Thaiand. Neighbouring districts are (from the south clockwise) Lamae and Phato of Chumphon Province, La-un of Ranong Province, and Sawi and Thung Tako of Chumphon Province.
The town of Lang Suan lies near the estuary of the Lang Suan River. The district has excellent transport links with both the north/south Highway 41 and Southern Railway main line passing through making it a possible stopover on this long distance route.