热塑性塑料（英语：thermoplastic，又译导热塑胶）指具有加热软化、冷却硬化特性的塑料。我们日常生活中使用的大部分塑料属于这个范畴。

热塑性聚合物是一种聚合物，指具有加热后软化、冷却时固化、可再度软化等特性的塑料。热塑性聚合物受热软化变成液态时具可塑性，冷却时则回到固态，因该现象可交替反复进行（有的物质只能受热可塑化一次，冷却固化后再受热则不具可塑性），所以可回收再利用；不同于热固性聚合物，后者在高温时不易软化也不容易发生形变(因此热固性聚合物虽能耐高温，却有无法回收的缺点)。

热塑性塑料中树脂分子链都是线型或带支链的结构，分子链之间无化学键产生，加热时软化流动，冷却变硬的过程是物理变化。

A thermoplastic, or thermosoftening plastic, is a plastic material, polymer, that becomes pliable or moldable above a specific temperature and solidifies upon cooling.

Most thermoplastics have a high molecular weight. The polymer chains associate through intermolecular forces, which weaken rapidly with increased temperature, yielding a viscous liquid. Thus, thermoplastics may be reshaped by heating and are typically used to produce parts by various polymer processing techniques such as injection molding, compression molding, calendering, and extrusion. Thermoplastics differ from thermosetting polymers, which form irreversible chemical bonds during the curing process. Thermosets do not melt, but decompose and do not reform upon cooling.