Gustav Ludwig Wilhelm Hinrichs[Note 1] (later Anglicized to Hinricks) (10 December 1850 - 26 March 1942) was a German-born American conductor and composer. He immigrated to the United States at the age of twenty, conducting opera in San Francisco, New York and Philadelphia where he founded his own opera company. His compositions include an opera and an accompanying score to the 1925 silent film The Phantom of the Opera.
Gustav Hinrichs was born in Grabow near Ludwigslust, Germany to August Hinrichs and Sophie née Havekoss. He studied music, first with his father, and later with Marxsen in Hamburg. At the age of fifteen he started studying conducting. By the age of twenty he was sufficiently accomplished to obtain a position as a conductor in the United States. Leaving from Hamburg via Le Havre, he arrived in the United States on the Silesia on 4 April 1870. In San Francisco he taught music and conducted the Fabbri Opera  and served as the music director of the Tivoli Opera House. One of the operas he directed there was The Prince of Pilsen by Henry W. Savage. In 1881 he founded the San Francisco Philharmonic Society, precursor of the San Francisco Symphony. His conducting of the newly established orchestra played to mixed reviews. While in San Francisco he conducted the Grand Military Band at the Authors' Carnival given for the Associated Charities of San Francisco, October 18 to October 28, 1880.
In 1888, he founded the Gustav Hinrichs Opera Company in Philadelphia which survived for ten seasons. On 28 July 1890, he produced and conducted the première of his own opera, Onti-Ora. He also conducted the American premières of Cavalleria rusticana (9 Sept. 1891), L'amico Fritz (8 June 1892), Les Pêcheurs de perles (1893) and Manon Lescaut (29 Aug. 1894). He conducted the première American performance of I Pagliacci in New York on 15 June 1893. He also conducted Hänsel und Gretel in Philadelphia
He moved back to New York where he conducted and held a professorship at Columbia University from 1895 to 1906 and taught at the National Conservatory. He conducted at the Metropolitan Opera for several seasons from 1899 to 1904 conducting Faust (19 Oct. 1899) at the house and Il Barbiere di Siviglia (14 Oct. 1899) while the Met was on tour in Syracuse, New York.
In addition to his opera, Hinrichs wrote an orchestral accompaniment to the 1925 silent film The Phantom of the Opera. The score was not ready for the première but was completed in time for its general release. He also wrote a symphonic suite and several compositions for voice.
Hinrichs was married to the soprano Katherine Fleming (b. Texarkana, Miller County, Arkansas, 27 Jan. 1870 - 10 Jul. 1939) in 1897. Twin girls, Irene Fleming and Julia Gustava, were born on 1 June 1899. His brothers Julius and August were a cellist and violinist respectively and both lived and played in San Francisco. August was the leader of the Ye Liberty Playhouse orchestra in Oakland, California. Gustav Hinrichs died in Mountain Lakes, New Jersey on 26 March 1942.