Oscar Greeley Clendenning Hammerstein II (/ˈhæmərstaɪn/; July 12, 1895 – August 23, 1960) was an American lyricist, librettist, theatrical producer, and director in musical theater for nearly 40 years.

He also collaborated with Jerome Kern (with whom he wrote the 1927 musical Show Boat), Vincent Youmans, Rudolf Friml, Richard A. Whiting, and Sigmund Romberg.

[6] Although Hammerstein's father managed the Victoria Theatre and was a producer of vaudeville shows, he was opposed to his son's desire to participate in the arts.

These included playing first base on the baseball team, performing in the Varsity Show and becoming an active member of Pi Lambda Phi fraternity.

[9][11] Following his graduation, he sat on the judging committee for the show and continued to contribute to several musicals, including Fly With Me, written by Richard Rodgers and Lorenz Hart.

[12] After quitting law school to pursue theater, Hammerstein began his first professional collaboration, with Herbert Stothart, Otto Harbach and Frank Mandel.

In 1927, Kern and Hammerstein wrote their biggest hit based on Edna Ferber's bestselling eponymous novel, Show Boat, which is often revived, as it is considered one of the masterpieces of American musical theater.

"[16] Many years later, Hammerstein's wife Dorothy bristled when she overheard someone remark that Jerome Kern had written "Ol' Man River".

Hammerstein also collaborated with Vincent Youmans (Wildflower), Rudolf Friml (Rose-Marie), and Sigmund Romberg (The Desert Song and The New Moon).

[18] Hammerstein's most successful and sustained collaboration began when he teamed up with Rodgers to write a musical adaptation of the play Green Grow the Lilacs.

[31] Hammerstein died of stomach cancer on August 23, 1960, at his home Highland Farm in Doylestown, Pennsylvania, aged 65,[32] nine months after the opening of The Sound of Music on Broadway.

[11][41] According to Stephen Sondheim, "What few people understand is that Oscar's big contribution to the theater was as a theoretician, as a Peter Brook, as an innovator.

"[44] According to The Rodgers and Hammerstein Story by Stanley Green, For three minutes, on the night of September first, the entire Times Square area in New York City was blacked out in honor of the man who had done so much to light up that particular part of the world.

A crowd of 5,000 people, many with heads bowed, assembled at the base of the statue of Father Duffy on Times Square where two trumpeters blew taps.

;[49] "If I Loved You" and "You'll Never Walk Alone" from Carousel, "Some Enchanted Evening", from South Pacific; "Getting to Know You"[50] and "Shall We Dance" from The King and I; and the title song as well as "Climb Ev'ry Mountain" from The Sound of Music.

[citation needed] Several albums of Hammerstein's musicals were named to the "Songs of the Century" list as compiled by the Recording Industry Association of America (RIAA), the National Endowment for the Arts, and Scholastic Corporation:[51] His advice and work influenced Stephen Sondheim, a friend of the Hammerstein family from childhood.