附带席位制（Additional Member System，AMS），又称「额外席位制」，是单一选区两票制的一种，与联立制、并立制相比，也是接近比例代表制的选举制度。

• 原指德国联立制、后来日本并立制的性质，即除单一选区外，另有比例代表制席次。换言之，就是单一选区两票制。
• 英国用来专指在威尔斯、苏格兰、伦敦实行的议会选举制度；日本也有同样选举改革方案，称为「小选区比例代表连用制」（小选挙区比例代表连用制）。

The Additional Member System (AMS), also known as Mixed-member proportional representation outside of the United Kingdom is a hybrid two-tier Mixed-Member Systems which varies in proportionality.

The term AMS is used in Scotland, Wales, and the London Assembly.