A black flag is the traditional international anarchist flag. It "negates all borders." Marcus Wendel, 13 August 1999
My personal consideration of the black flag is that it denotes "allegiance to nothing higher." Plain black represents total absence of allegiance. Solver Hafsteinn Hafsteinsson, 19 May 2000
The black flag is very much a traditional flag. There is no official version of its significance, of course. It has been said to symbolize the negation of national flags, solemnity, resolve and mourning. It is also a symbol of unity (all colours in one) and strength. Some suggest it was an adaptation of the pirate flag. Matthias Speer, 5 February 2003
Regarding the symbolism of the colour black:
Dried blood
Hunger, misery and death
The anarchist black flag is supposed to have been first used during the Paris Commune of 1871 by Louise Michel and has since been used by various anarchist organizations since. Marcus Wendel, 16 August 1999
This is historically incorrect, possibly a myth associated to the mythical Louise Michel:
the flag hoisted by the Communards on the City Hall of Paris was the red flag [pst98]
Louise Michel was not yet an anarchist in 1871. After the defeat of the Paris Commune, during which she had administrated the Revolution Club, she was sentenced to deportation. She arrived in New Caledonia in 1873, and began to educate the Kanaks and support them in their revolt against the colonials. She herself dates from this period her adhesion to anarchist ideas. She received amnesty in 1880 and came back triumphantly to Paris (and was later nicknamed the "Red Virgin"). Then she became the mythic voice of the workers' movement and anarchism. She died in 1905. (Source: Encyclopaedia Universalis, CD-ROM edition)
Ivan Sache, 16 August 1999
Historically, anarchists have made alliances with communist and socialist movements for tactical purposes — e.g. fighting the Austro-German occupation of Ukraine: At one point, Maqno's insurgent army was integrated into the Red Army, but was allowed to keep its black flags. Matthias Speer, 5 February 2003