三院制（英文：Tricameralism），即是指由三个议院组成的议会，与现时常见的一院制与两院制相比，三院制与四院制均十分罕见。

南非1983年宪法中，基于种族隔离政策，白人、黑人和亚洲人就分开选出三个议院。

拉丁美洲革命家西蒙·玻利瓦理想中的政府，亦由三个议院组成。一个普选的院负责行政，一个世袭的院负责立法，还有一个负责监察上述两院。但拉丁美洲国家独立后受美国影响，大部分行两院制。

法国大革命前的法国旧制度亦是三院制，即三级会议。三个院分别由教士、贵族和平民组成。

Tricameralism is the practice of having three legislative or parliamentary chambers. It is contrasted to unicameralism and bicameralism, both of which are far more common.

The term was used in South Africa to describe the Parliament established under the apartheid regime's new South African Constitution of 1983. Other instances of tricameral legislatures in history include Simón Bolívar's model state. The word could also describe the French Estates-General, which had three 'estates'.