私掠许可证（英语：Letter of Marque and Reprisal）是16至19世纪间，西方许多海权强国授权给指定的航海家，允许他们可以针对本国以外的违法人士、船队进行追捕、摧毁等私掠行为的一种特许证或委任状。除了上述权力之外，私掠许可证常常还允许攻击、掠夺敌国的商船。拥有私掠许可证的船队称为私掠船。

1856年，克里米亚战争结束后缔结了巴黎条约，同年4月16日发表巴黎宣言，以附件追加的形式废止了私掠权限，但当时主要只剩下美国未批准此合议。直到1907年，含美国在内的列强在海牙和会中决议武装商船必须视为军舰造册管理之后，私掠许可证的历史才正式画下句点。

In the days of fighting sail, a letter of marque and reprisal was a government license authorizing a person (known as a privateer) to attack and capture enemy vessels and bring them before admiralty courts for condemnation and sale. Cruising for prizes with a letter of marque was considered an honorable calling combining patriotism and profit, in contrast to unlicensed piracy, which was universally reviled. In addition to the term lettre de marque, the French sometimes used the term lettre de course for their letters of marque. "Letter of marque" was sometimes used to describe the vessel used: a "letter of marque" generally refers to a lumbering square-rigged cargo carrier that might pick up a prize if the opportunity arose. A "privateer" was a fast and weatherly fore-and-aft-rigged vessel heavily armed and heavily crewed, intended exclusively for fighting.