聚酯（Polyester）是一类在其主链上含有酯基官能团的聚合物。虽然聚酯有很多种，但是“聚酯”一词通常指的是聚对苯二甲酸乙二酯（PET）。

聚酯包括天然化合物如植物角质，以及通过逐步缩合而成的合成纤维如聚碳酸酯和聚（对苯二甲酸/己二酸）乙二酯。天然聚酯和一部分合成聚酯是可以生物降解的，但绝大部分合成聚酯都不会被生物降解。

聚酯可分为「饱和聚酯」和「不饱和聚酯」两大类，通常由一种或多种多元酸（酸酐）与一种或多种多元醇经缩聚制得。

Polyester is a category of polymers that contain the ester functional group in their main chain. As a specific material, it most commonly refers to a type called polyethylene terephthalate (PET). Polyesters include naturally occurring chemicals, such as in the cutin of plant cuticles, as well as synthetics through step-growth polymerization such as polybutyrate. Natural polyesters and a few synthetic ones are biodegradable, but most synthetic polyesters are not. This material is used very widely in clothing.