《1811年精神病人婚姻法令》（英语：Marriage of Lunatics Act 1811）是在英国国王乔治三世在位期间实施的英国议会法令，旨在“防止精神病人结婚”（to prevent the marriage of Lunatics），并使法令生效日期之前、当日或之后所有与精神病人缔结的婚姻，不论是否为婚前获诊断，“就所有用意及目的而言，均属作废及无效”（null and void to all intents and purposes whatsoever）。
该法令内容如下：
Whereas an Act was made in the Parliament of Great Britain in the fifteenth year of the reign of his late Majesty King George the Second to prevent the marriage of lunatics: And whereas it is expedient that the provisions of the said Act should be extended to Ireland: Be it therefore enacted by the King’s most excellent Majesty, by and with the advice and consent of the lords spiritual and temporal, and commons, in this present Parliament assembled, and by the authority of the same, that from and after the expiration of ten days after the passing of this Act, in case any person who has been or at any time hereafter shall be found a lunatic by any inquisition taken or to be taken by virtue of a commission under the great seal of Great Britain or the great seal of Ireland respectively, or any lunatic or person under a phrenzy, whose person and estate by virtue of any Act of Parliament now or hereafter shall be committed to the care and custody of particular trustees, shall marry before he or she shall be declared of sane mind by the lord high chancellor of Great Britain or Ireland or the lord keeper or lords commissioners of the great seal of Great Britain or Ireland for the time being or such trustees as aforesaid or the major part of them respectively, as the nature of the case shall require, every such marriage shall be and is hereby declared to be null and void to all intents and purposes whatsoever.
2021年，该法令于《2015年受助作决定（行为能力）法令》（Assisted Decision-Making (Capacity) Act 2015）生效日期当日被完全废除。
