Robert Merrill (4 June 1919 - 23 October 2004; some sources give his birth year as 1917) was an American opera baritone. Merrill was born Moishe Miller in Brooklyn, New York, to shoe salesman Abraham Merrill, né Millstein, and his wife Lillian, née Balaban, immigrants from Warsaw. Lillian had had an operatic and concert career in Poland and gave her son early voice training: he had a tendency to stutter, which disappeared when singing. Merrill was inspired to pursue professional singing lessons when he saw a performance at the Metropolitan Opera, and paid for them with money earned as a semi-professional pitcher. In his early radio appearances as a crooner he was sometimes billed as Merrill Miller. Singing at bar mitzvahs and weddings and at hotels in the Catskills he met an agent, Moe Gale, who found him work at Radio City Music Hall and with the NBC Concert Orchestra , and obtained Merrill's operatic debut in Verdi's Aida in Newark, New Jersey.

Merrill, who had continued his vocal studies under Samuel Margolis made his debut at the Metropolitan Opera one year later, in 1945, as Germont in La Traviata. His appearance in the hillbilly movie Aaron Slick from Punkin Crick led to conflict with Rudolf Bing and a brief departure from the Met in 1951. Merrill sang many different baritone roles, becoming, after the on-stage death of Leonard Warren in 1960, the Met's principal baritone. He was described by TIME as "one of the Met's best baritones". He also continued to perform on radio and television, in nightclubs and recitals. He retired from the Met in 1976.

He married soprano Roberta Peters in 1952. They parted amicably; he had two children, a son David and a daughter Lizanne, with his second wife, Marilyn, née Machno, a pianist.

He wrote two books of memoirs, Once More From the Beginning (1965) and Between Acts (1976), and co-wrote a novel, The Divas (1978).

Relatively late in his singing career, Merrill also became known for singing The Star-Spangled Banner at Yankee Stadium. He first sang the national anthem to open the 1969 baseball season and it became a tradition for the Yankees to bring him back each year on Opening Day . Merrill preferred a traditional approach to the song devoid of additional ornamentation; he told Newsday in 2000, "When you sing the anthem, there's a legitimacy to it. I'm extremely bothered by these different interpretations of it."

Merrill received the National Medal of Arts in 1993.