James Elliot Lapine (born January 10, 1949) is an American stage director, playwright, screenwriter, and librettist. He has won the Tony Award for Best Book of a Musical three times, for Into the Woods, Falsettos, and Passion, as well as the Pulitzer Prize for Drama for Sunday in the Park with George. He has frequently collaborated with Stephen Sondheim and William Finn.

Lapine was born on January 10, 1949, in Mansfield, Ohio, the son of Lillian (Feld) and David Sanford Lapine. He graduated from Franklin and Marshall College in 1971. Though he did not actively pursue theatre in childhood, Lapine did play Jack in an elementary school production of Jack and the Beanstalk.

Lapine studied photography and graphic design at the California Institute of the Arts, where he received an MFA in 1973. He was a photographer, graphic designer, and architectural preservationist, and taught design at the Yale School of Drama. At Yale University he wrote an adaptation of and directed Gertrude Stein's Photograph, which was produced Off-Broadway at the Open Space in SoHo in 1977. He went on to write and direct Off-Broadway plays and musicals, directing composer William Finn's March of the Falsettos in 1981; the musical won the Outer Critics Circle Award for Best Off-Broadway Play. Frank Rich, the New York Times theater critic, noted "Mr. Lapine's wildly resourceful staging".

In 1982, Lapine was introduced to Stephen Sondheim. The pair developed Sunday in the Park with George: Lapine wrote the book and directed; Sondheim created the music and lyrics. The play was first produced Off-Broadway in 1983, and moved to Broadway in 1984. Their next musical was Into the Woods, which premiered on Broadway in 1987, for which Lapine won the Tony Award and the Drama Desk Award for Best Book of a Musical. They next collaborated on the musical Passion, for which Lapine wrote the book and directed. The musical ran on Broadway in 1994 and in the West End in 1996, receiving a nomination for the Olivier Award for Best New Musical, and winning the Tony Award for Best Musical and the Tony Award for Best Book of a Musical, among other awards and nominations. Their last collaboration was the revue Sondheim on Sondheim. Presented on Broadway in 2010, it won the Drama Desk Award for Outstanding Musical Revue.

In 1992, Lapine returned to working with William Finn, and wrote the book and directed the Broadway musical Falsettos. Lapine wrote the book and Finn composed the music for A New Brain, which premiered Off-Broadway in 1998. They later worked together on Finn's musical The 25th Annual Putnam County Spelling Bee, which premiered Off-Broadway in 2005 and later moved to Broadway. The New York Times reviewer wrote of the Spelling Bee Broadway transfer that "Mr. Lapine has sharpened all the musical's elements without betraying its appealing modesty." The latest Finn-Lapine work is Little Miss Sunshine, which premiered in 2011 at the La Jolla Playhouse in California.

Lapine has also directed dramas, including Dirty Blonde, which ran Off-Broadway and then on Broadway in 2000. Conceived by Claudia Shear and Lapine and written by Shear with direction by Lapine, Ben Brantley called Lapine's direction "stylish and compassionate". Lapine was nominated for the Tony Award and Drama Desk Award for Best Direction of a Play.

Lapine directed the 2012 Broadway revival of Annie. He wrote a stage adaption of the Moss Hart autobiography Act One, which premiered on Broadway at the Lincoln Center Vivian Beaumont Theater in April 2014.

Lapine wrote the book for and directed the new musical Flying Over Sunset. A staged singing/reading was presented at the Vineyard Arts Project (Martha's Vineyard) in August 2015. The composer is Tom Kitt and lyrics are by Michael Korie. The musical premiered on Broadway at the Vivian Beaumont Theater on November 11, 2021 in previews with the official opening scheduled for December 13. The production was originally scheduled to open on April 16, 2020, but was postponed due to the COVID-19 pandemic.