John Alexander (October 21, 1923 – December 8, 1990) was an American operatic tenor who had a substantial career during the 1950s through the 1980s. He had a longstanding relationship with the Metropolitan Opera in New York City, singing with that company every year between 1961 and 1987 for a total of 379 performances. He also periodically performed at the New York City Opera during his career and was a frequent presence at the Philadelphia Lyric Opera Company during the late 1950s and 1960s. Although he spent most of his career in New York City, Alexander occasionally traveled to perform as a guest artist with many of the world's leading opera houses, both in the United States and Europe. He was also an active concert singer throughout his career.

While most of Alexander's career was spent in lyric roles from the Italian and French repertory, he had enough heft in his voice to successfully tackle some of the lighter Heldentenor roles of Richard Wagner and Richard Strauss. Aside from a handful of these roles, however, his repertoire at the Metropolitan did not include heavier parts. Rather, he was known there for an expansive lyric repertoire that encompassed the works of Mozart, Puccini, Verdi, and Donizetti among others. His signature roles included Alfredo in La traviata, Arbace in Idomeneo, Belmonte in Die Entführung aus dem Serail, the Duke of Mantua in Rigoletto, Edgardo from Lucia di Lammermoor, Ferrando in Così fan tutte, Hoffman in Les contes d'Hoffmann, Lieutenant B. F. Pinkerton in Madama Butterfly, Rodolfo in La bohème, and the title roles in Don Carlos and Faust.