In 1785, a young American named James Leander Cathcart is kidnapped at sea and carried as prisoner to the maverick North African statelet of Algiers. The piratical corsairs of Algiers have decided to exploit the vulnerability of the United States by seizing its mariners and holding them for ransom. Today, the name of James Leander Cathcart has been all but forgotten. The Lionkeeper of Algiers reveals the extraordinary and unlikely story of Cathcart, who rose steadily up the ranks from lionkeeper at the Dey's private zoo to become Chief Clerk at the Palace, along the way amassing a chain of taverns in Algiers that functioned as safe houses and food banks for American prisoners. Eleven years later, Cathcart was paroled back to America and charged with delivering a vital letter to President George Washington, saving a tenuous peace deal and bringing the other captives home. Cathcart would go on to become a US diplomat in the lands where he was held captive for more than a decade. This narrative follows the twists and turns of Cathcart's own life upon the international stage of diplomacy, trade, and maritime statecraft at a time when America's place in the world was hanging in the balance.