四氢噻吩（THT）即“硫杂环戊烷”，是噻吩经催化氢化后得到的五元饱和含硫杂环化合物。

四氢噻吩是无色透明有挥发性的液体，有强烈的不愉快气味。不溶于水，可混溶于乙醇、乙醚、苯、丙酮。

噻吩被还原为四氢噻吩后，不再具有共轭体系和芳香性，因此四氢噻吩显示出一般硫醚的性质，易于氧化为亚砜和砜（环丁砜）。

Tetrahydrothiophene is an organosulfur compound with the formula (CH₂)₄S. It consists of a five-membered ring containing four carbon atoms and a sulfur atom. It is the saturated analog of thiophene. It is a volatile, colorless liquid with an intensely unpleasant odor. It is also known as thiophane, thiolane or THT.