P. P. Werlein was an American music publisher based in New Orleans, Louisiana. At some point, the German-born Philip P. Werlein headed the music department at the Female Seminary of Clinton, Mississippi. However, music publishing became his main business when he entered the field in 1842 in Vicksburg, Mississippi. In 1853, he moved operations to New Orleans, where he established a company called Ashbrand & Werlein at 93 Camp Street. The name changed to P. P. Werlein the following year. He listed his address variously as 3 and 5 Camp Street and 172 Canal Street (before the 1894 street address renumbering).
Like much of the mid-19th century U.S. music industry, Werlein showed little respect for copyright during his career. In 1860, he published unauthorized sheet music for the blackface minstrel hit, "Dixie". Only the threat of legal action convinced Werlein to credit Dan Emmett as the song's writer and to pay royalties to Firth, Pond & Co. Emmett, perhaps sardonically, dedicated the "Dixie" sequel, "I'm Going Home to Dixie", to Werlein in 1861.
At the outbreak of the American Civil War, Werlein became a vocal proponent of the Confederacy. He refused to recognize Union copyrights and published new versions of "Dixie", including "The War Song of Dixie" with words by Albert Pike. He also profited from pro-Confederate sentiment by publishing several pieces of music attributed falsely to Jefferson Davis. The Civil War also brought the addition of Werlein's wife's name to the company, which became P. P. Werlein & Halsey in 1861. Nevertheless, the the collapse of Confederate money with the end of the Civil War put Werlein out of business.
P. P. Werlein & Halsey reopened in 1865. Philip Werlein's son, also named Philip, became the new owner. Many years later, the business fell to Philip Werlein, Jr.'s son. In 1940, David Franck bought the Werleins' publishing business, but the family kept their retail store open in New Orleans. The chain of Werelein's Music Stores continued in Greater New Orleans until the start of the 2000s.