Lang Suan (Thai: หลังสวน, pronounced [lǎŋ sǔa̯n]) is a district (amphoe) of Chumphon province, southern Thailand.

Lang Suan was originally a mueang reporting directly to Bangkok.

During the Thesaphiban reforms at the end of the 19th century it was put under monthon Chumphon.

On 29 April 1917 the district's name was changed from Mueang Lang Suan to Khan Ngein (ขันเงิน).

The town (thesaban mueang) Lang Suan includes the tambon Lang Suan and parts of Khan Ngoen, Pho Daeng, Laem Sai, and Wang Tako.