Giacomo Puccini was a Human opera composer from Italy in the 19th century. Among his best works is La bohème, from which The Doctor performed the aria O, soave fanciulla in 2373. (VOY: "The Swarm")
Another of his works was Tosca, which was performed at the Dorothy Chandler Pavilion in Los Angeles in 1996. (VOY: "Future's End, Part II") Tosca made The Doctor sob throughout its third act the first time he saw it. (VOY: "Imperfection")
The Doctor called himself a "night-owl" as he would listen to Puccini from time to time at night in sickbay. When crewmembers had to sleep in his sickbay, in order to save energy, he was concerned that someone might snore while he was listening to the music. (VOY: "Demon")
According to the Star Trek Encyclopedia (4th ed., vol. 2, p. 188), the birth and death years of Giacomo Puccini were 1858 and 1924, respectively.