缩硫醛（英语：Thioacetal）是缩醛的硫类似物，由醛与硫醇反应而得。其中又分为单缩硫醛和双缩硫醛，分别是醛与一分子醇、一分子硫醇或醛与两分子硫醇缩合的产物。缩硫醛/缩硫酮具有特殊的极性翻转性质，可用于合成。

Thioacetals are the sulfur analogues of acetals. There are two classes: monothioacetals and dithioacetals. Monothioacetals are less common, have the functional group RC(OR')(SR")H. Dithioacetals have the formula RC(SR')₂H (symmetric dithioacetals) and RC(SR')(SR")H (asymmetric dithioacetals).