The Brotherhood of Blackheads (Estonian: Mustpeade vennaskond; German: Bruderschaft der Schwarzhäupter; Latvian: Melngalvju brālības) is an association of local unmarried merchants, ship owners, and foreigners that was active in Livonia (present-day Estonia and Latvia) from the mid-14th century till 1940 but still remains active in present day Hamburg. The Brotherhood of Blackheads was founded as a military organization but the non-military aspects of the association gradually became more pronounced until the Brotherhood became a predominantly social organization after the end of the Great Northern War.
The brotherhood traces its origin to a group of foreign merchants who, according to the legend, had participated in the defense of Reval (present-day Tallinn in Estonia) during the St. George's Night Uprising between 1343 and 1345 when the indigenous population of Estonia unsuccessfully tried to exterminate all foreigners and eradicate Christianity from Estonia. The earliest documented mention of the Brotherhood comes in an agreement with the Tallinn Dominican Monastery from 28 March 1400 that confirms the Blackheads' ownership of all the sacred church vessels that they had deposited in the St. Catherine's Church of the Dominicans. In the same agreement the Blackheads commit themselves to decorating and lighting the altar of St. Mary that the brotherhood had commissioned for the church, and the Dominicans in their turn undertake to hold services in front of this altar to bless the souls of the Blackheads. On 12 September 1407, the Tallinn City Council ratified the statutes of the Brotherhood, also known as the Great Rights. The statutes of the Brotherhood in Riga date back to 1416.