Florencio Constantino (April 9, 1869 – November 19, 1919) was a Spanish operatic tenor who had an active international performance career from 1892 through 1917. He was particularly admired for his performances in the operas of Giuseppe Verdi and Vincenzo Bellini; with the roles of the Duke of Mantua in Rigoletto and Arturo in I puritani being signature roles for the tenor.

Raised primarily in Argentina, Constantino began his career performing in opera houses in South America from 1892-1897 before traveling to Spain to pursue vocal training with Leopoldo Stiatesi. From 1898-1900 he appeared in leading roles in opera houses in Italy, Spain, Germany, Poland, and Russia and then resumed performing in opera houses in South America during the first years of the 20th century. He returned to Europe for a tour of Spain and Germany in 1903-1904 and then became a resident artist at the Theater des Westens in Berlin in 1904-1905.

In 1905 Constantino was committed to the Royal Opera House in London before joining English impresario Henry Russell's touring San Carlo Opera Company; a company with whom he toured the United States in 1906-1907. In 1908 he joined Oscar Hammerstein I's Manhattan Opera Company and in 1909 he became the principal tenor of the newly created Boston Opera Company; a company with whom he performed until it closed in 1915. In 1910 he made his debut with the Metropolitan Opera.

After the closing of the Boston Opera Company, Constantino moved to Los Angeles where he served as the Artistic Director of the California Grand Opera Company in 1916. In 1917 a disastrous appearance at the Saint Louis Opera led to a highly publicized lawsuit against Constantino. He left the United States for Mexico City where he suffered a mental breakdown and died at a hospital for the destitute in 1919.