原子层沉积（英文：Atomic layer deposition）是一种可以将物质以单原子膜形式一层一层的镀在基底表面的方法。原子层沉积与普通的化学沉积（化学气相沉积）有相似之处。但在原子层沉积过程中，新一层原子膜的化学反应是直接与之前一层相关联的，这种方式使每次反应只沉积一层原子。原子层沉积的主要反应物有两种化学物质，通常被称作前驱物。

原子层沉积的示意图：

Atomic layer deposition (ALD) is a thin film deposition technique that is based on the sequential use of a gas phase chemical process. ALD is considered a subclass of chemical vapour deposition. The majority of ALD reactions use two chemicals, typically called precursors. These precursors react with the surface of a material one at a time in a sequential, self-limiting, manner. Through the repeated exposure to separate precursors, a thin film is slowly deposited. ALD is a key process in the fabrication of semiconductor devices, and part of the set of tools available for the synthesis of nanomaterials.