Phi Mu Alpha Sinfonia (also known as Phi Mu Alpha, or simply Sinfonia) is an American collegiate socialfraternity for men with a special interest in music. The fraternity is open to men "who, through a love for music, can assist in the fulfillment of [its] Object and ideals either by adopting music as a profession, or by working to advance the cause of music in America." Phi Mu Alpha has initiated more than 150,000 members, known as Sinfonians, and the fraternity currently has almost 6,000 active collegiate members in 239 collegiate chapters throughout the United States.

Phi Mu Alpha Sinfonia was founded as the Sinfonia Club at the New England Conservatory of Music in Boston, Massachusetts on October 6, 1898, by Ossian Everett Mills, bursar of the conservatory. Exactly two years later, on October 6, 1900, a delegation of members from the Sinfonia Club visited the Broad Street Conservatory of Music in Philadelphia, Pennsylvania, and a group of students there petitioned to form a chapter of the club, thus establishing the organization as a national fraternity. By 1901, two additional chapters had been formed and the 1st National Convention was held in Boston to establish a national constitution.