Rostam Batmanglij (born November 28, 1983) is an American songwriter, composer, producer and multi-instrumentalist of New York-based indie rock band Vampire Weekend and electro-soul group Discovery.
Batmanglij grew up in Washington D.C. His mother is cookbook author Najmieh Batmanglij while his father is a publisher. His parents are both Iranian and arrived in D.C. in 1983. His brother is independent filmmaker Zal Batmanglij. The two collaborated on the film, Sound of My Voice, which Rostam scored and which Zal directed and co-wrote. Rostam also composed an original piece for piano that was featured in Zal's film The East.
Batmanglij majored in music at Columbia University where Vampire Weekend formed in 2006. "At Columbia, I would study classical harmony in classes and I would study music on my own, and I would try to re-create songs that I love in recordings...that was really how I learned." The name of the group comes from the movie of the same name that bandmate Ezra Koenig and his friends made over summer vacations. Batmanglij produced their self-titled debut album shortly after graduation while concurrently working multiple full-time jobs. He also produced the band's follow up album, Contra which sold 124,000 copies in its first week and landed atop the Billboard 200 charts. Batmanglij plays guitar, keyboard and sings in the band but also acts as a lyricist and songwriter, co-writing the song "Diplomat's Son" on Contra. Koenig has described himself and Batmanglij as "the two main songwriters in the band." 
Batmanglij began recording with Ra Ra Riot's vocalist Wes Miles on a project which was later to become Discovery. They released their debut album LP on July 7, 2009 on XL Recordings. The album features guest vocal contributions from Koenig as well as Dirty Projectors' Angel Deradoorian.
In September 2011, Batmanglij released a solo track called "Wood". Timeout Chicago's Brent DiCrescenzo gave the song 4 out of 5 stars and wrote that "his voice pleasantly recalls a drowsy David Byrne". On November 1, 2011, Zane Lowe debuted another a solo song sung by Batmanglij called "Don't Let it Get to You" as the Hottest Record in the World on BBC Radio1. The Fader referred to it as "a seismic event of a song.".
On March 18, 2013, Vampire Weekend released two songs from their album Modern Vampires of the City, "Diane Young" and "Step". Within two weeks each song had garnered more than 1 million views on YouTube. Music for both songs is credited to Batmanglij and Koenig, and lyrics are credited to Koenig. Modern Vampires of the City is the first Vampire Weekend album Batmanglij did not produce alone; for this record he collaborated with longtime friend Ariel Rechtshaid and the two co-produced the album together. It was released May 14, 2013.
Batmanglij produced and co-wrote two songs for The Walkmen frontman Hamilton Leithauser's forthcoming solo album which is expected to be released in 2014.