Edward Darcy Esquire v Thomas Allin of London Haberdasher (1602) 74 ER 1131 (also spelt as "Allain" or "Allen" and "Allein" but most widely known as the Case of Monopolies), was an early landmark case in English law, establishing that the grant of exclusive rights to produce any article was improper (monopoly).

The reasoning behind the outcome of the case, which was decided at a time before courts regularly issued written opinions, was reported by Sir Edward Coke.

This arrangement was apparently secured in part by the Queen's concern that card-playing was becoming a problem among her subjects and that having one person control the trade would regulate the activity.

When the defendant, Thomas Allin, a member of the Worshipful Company of Haberdashers, sought to make and sell his own playing cards, Darcy sued, bringing an action on the case for damages.

For we read in Justinian that monopolies are not to be meddled with, because they do not conduce to the benefit of the common weal but to its ruin and damage.