Josephine Decker (born April 2, 1981) is an English–born American filmmaker. Films she has directed include Butter on the Latch (2013), Thou Wast Mild and Lovely (2014), Madeline's Madeline (2018), Shirley (2020), The Sky is Everywhere (2022), and Chasing Summer (2026). She also co-directed the documentary Bi the Way (2008) with Brittany Blockman.

Decker was born in London and raised in Texas. As a child, she played the piano and dreamed of being a writer, as well as a photographer for National Geographic. She graduated from Highland Park High School in 1999 and Princeton University in 2003, where she aspired to become a conductor and applied for a conducting class. She was inspired to become a filmmaker after watching Monsters, Inc.

Decker produced and directed her first short film, Naked Princeton, in 2005.

In 2008, Decker and Brittany Blockman co-directed the documentary Bi the Way, which focuses on bisexuality in the United States. Despite being described by Variety's Joe Leydon as a "once-over-lightly examination of an alleged cultural phenomenon", the film won the Alternative Spirit Grand Prize at the Rhode Island International Film Festival.

Decker wrote and directed her second short film, Where Are You Going, Elena?, in 2009. In 2012, she wrote and directed the short film Me the Terrible, which Richard Brody of The New Yorker called a "wondrous short film".

In May 2010, Decker attended the last day of Marina Abramović's retrospective The Artist Is Present at MoMA. As she sat down across from Abramovic, Decker immediately disrobed and stood naked in the middle of the museum until seven security guards escorted her out over the museum's no-nudity policy. Decker declared that her goal was to be "as vulnerable to [Abramovic] as she constantly makes herself to us."

In 2013, Decker wrote, produced, and directed her first feature film, the experimental psychological thriller Butter on the Latch. Eric Kohn of Indiewire wrote that Decker's career was "one to keep an eye on" and Peter Debruge of Variety wrote, "Decker has fashioned the kind of feature debut the film industry simply doesn't support, but would do well to encourage: a visually poetic, virtually free-form groove in which emotion, rather than narrative, guides viewers through a young woman's visit to a Balkan folk music camp." Decker was included in Filmmaker Magazine's 2013 list of 25 New Faces in Independent Film.

In early 2014, she completed her second theatrical film, the experimental erotic thriller Thou Wast Mild and Lovely, starring Sophie Traub and Decker's frequent collaborator Joe Swanberg. To raise money for the film's post-production, Decker ran a crowdfunding campaign on Kickstarter with a goal of $15,500. The campaign closed on August 22, 2013, having raised $18,517. In his review, Kohn gave the film a B+, writing, "Its labyrinthine characteristics suggest the unholy marriage of Ingmar Bergman and David Lynch. While nowhere near the same level of refinement as those giants, Decker concocts a wholly enveloping vision of isolation told with a grimly poetic style that wanders all over the place but never stops playing by its own eerie rulebook."