Who were the Barbary Pirates?

"Barbary Pirates", "Barbary States", etc., are collective terms we use to refer to the Deys, Beys, and other rulers of nominally Ottoman-controlled regions on the North African coast (referred to as the Barbary Coast). In the context of conflict with the United States, it refers to pirates/privateers operating out of port cities in Morocco, and the cities of Algiers, Tunis, and Tripoli.

Largely autonomous, these pirates/privateers (I've seen them referred to as both, I'll let our pirate historians grapple over the proper terminology!) had operated largely in the Mediterranean since the 16th Century against the shipping of the European Christian nations. Their attacks often resulted in the enslavement of captured crews, but they were not unlike the more media-exposed Caribbean pirates in that their principal motives were economic gain through extortion and ransom of captured crews and ships. A unique factor is that the Barbary pirates were operating out of de facto states, and so the Deys and Beys (leaders) of these port regions would often make demands directly to the nations they were raiding, pressing for tribute in exchange for a cessation in maritime attacks. Though they did have the religious angle of their Islamic status, believing themselves to be at war with any non-Muslim nation that had not negotiated tribute, their motives were primarily economic. European nations had a history of leading armed expeditions against these raiders, but for the most part had settled on paying the demanded tribute instead of the economic drain of constantly patrolling routes in the Mediterranean.

When the United States was beginning it's young existence as an independent country, it's merchant shipping was no longer under protection of the Royal Navy, and later souring of relations with France (including the maritime Quasi-War of 1798-1800) also meant that they could not count on the support of it's chief ally in the Revolution. When Barbary Pirates began to seize American vessels and capture American crews in the 1780s, the United States was largely powerless to stop them. The demands of the Barbary Pirates were either economically unrealistic to the United States or simply refused, and negotiations would move at a frustrating pace. Uneasy truces, settlements, and payments were negotiated with the Barbary rulers in the 1790s. The impetus to end piracy against American merchants, as well as developments in Europe, would launch the creation of a permanent United States Navy (the famed Six Frigates) and Navy Department.

Edit: Not just going to leave my answer at that, I will discuss the Barbary Wars when I return from some IRL things I have to attend to. Stay tuned!

You've got the makings of a damn fine answer already but ill add a few things in the mean time. First it isnt really talked about much because in the end it didnt really have any lasting impact. Our Navy ran the war on a shoestring budget and basically got lucky and to a large extent annoyed and confounded the various Beys and Deys into either calling off their pirates or signing treaties less detrimental to the US and commerce went on as before until 1812.

Much like the Quasi-War with France it never involved more then a few dozen warships at any one time and will containing some incredible feats of personal bravery, like Decatur's burning of the captured frigate Philadelphia, the security of the nation was never in serious jeopardy.

Finally if you have ever heard the words to the Marine's Hymn, youve heard a reference to it in the line "From the Halls or Montezuma, to the Shores of Tripoli" referencing the Mexican and Barbary Wars respectively, and an incredible feat of resilience which I think the other poster should have the pleasure telling the story.

The book Six Frigates: The Epic History of the Founding of the US Navy by Ian Toll is a great source for both the lead up and conduct of the war.