分子晶体指的是物质内部由范德华力（又称作范德瓦耳斯力或分子间作用力）将分子结合起来的固体物质。

晶体的内部由分子构成，大多数非金属单质（少数如Si等除外）、它们的化合物以及大多数有机物在处于固态时都属于分子晶体。其内部各个分子间由一种不是化学键的分子间作用力相互吸引，结合成晶体。

A molecular solid is a solid composed of molecules held together by the van der Waals forces. Because these dipole forces are weaker than covalent or ionic bonds, molecular solids are soft and have relatively low melting temperature. Molecular solids can be amorphous solids or crystals. Examples of molecular solids include hydrocarbons, ice, sugar, fullerenes, sulfur, and solid carbon dioxide. Pure molecular solids are electrical insulators but they can be made conductive by doping.