Several allegations of unlawful campaigning in the 2016 EU referendum have been made. Some allegations were dismissed by the investigating bodies, but in other cases wrongdoing was established, leading to the imposition of penalties. Sanctions have included the levying of the maximum fine possible on Facebook for breaches of data privacy.
Several institutions have investigated the allegations: the Information Commissioner's Office (regarding the handling of personal data); the Electoral Commission (regarding penalising breaches of electoral law); the National Crime Agency; the Metropolitan Police, and Crown Prosecution Service (regarding criminal prosecution); the UK Parliament; the European Parliament; and the Venice Commission; there have also been private prosecutions.