Lithium–sulfur (Li–S) batteries are widely regarded as one of the promising next-generation secondary energy storage systems. However, some tricky challenges, such as electrically insulating elemental sulfur, shuttle effect and lithium dendrites, have been limiting its practical application. Modification of separators, which is found as a facile and low-cost settlement, has shown great advantages in solving the above three crucial problems, leading to greatly improved performance of Li–S batteries. In this paper, we summarize recent progresses on separators for Li–S batteries including coatings such as carbon materials, polymers, and inorganic materials, and tailoring multi-functional gel separators to achieve Li–S batteries with high performance. The importance and development directions of functional separators in the further commercialization of Li–S batteries are also discussed.