围标，指以一家企业在投标过程中通过人为操纵，从而实现中标或等同的实际目的。围标在中国大陆属于犯罪行为。在通常的投标过程中，所有单位之间没有直接的利益关系，通过技术(技术标)、综合实力(综合标)、价格报价(商务标)三个考核标准相互竞争，优胜劣汰。但是当一个项目被“围标”之后，就会出现几家企业串通一气。一致以其中一家企业中标为目的，通过集体编撰虚假标书内容，蓄意扰乱投标价格规律等手段打破平等竞争的前提条件，通过舞弊的方式完成投标过程。

Bid rigging is a form of fraud in which a commercial contract is promised to one party even though for the sake of appearance several other parties also present a bid. This form of collusion is illegal in most countries. It is a form of price fixing and market allocation, often practiced where contracts are determined by a call for bids, for example in the case of government construction contracts.