Edie & Thea: A Very Long Engagement is a 2009 American documentary film directed and produced by Susan Muska and Gréta Ólafsdóttir for their company Bless Bless Productions, in association with Sundance Channel. The film tells the story of the long-term lesbian relationship between Edie Windsor and Thea Spyer, including their respective childhoods, their meeting in 1963, their lives and careers in New York City, Thea's diagnosis with multiple sclerosis and Edie's care for her partner, and their wedding in Toronto, Canada, in May 2007, because gay marriage was not then legal in their home state of New York.

Upon its initial release, the film was screened primarily at LGBTQ film festivals in 2009 and 2010. The Edie in the film's title was Edith Windsor, who after the death of Thea Spyer on February 5, 2009, was hit with an estate tax bill of $363,053 from the IRS. Had Thea been a man, Edie would have been exempt from this tax due to the marital exception. But the U.S. Defense of Marriage Act (DOMA), which defined marriage as limited to a man and a woman, was in effect at the time. Windsor filed suit against the federal government on November 9, 2010, which ultimately made its way to the Supreme Court of the United States as United States v. Windsor. In June 2013, the Supreme Court upheld the lower court rulings in Windsor's favor and declared that DOMA was unconstitutional.

During the course of the various court cases, the film garnered even more attention and was screened at mainstream film festivals, Jewish film festivals, churches, colleges and universities, libraries, and many other events and locations including a cruise ship. The documentary has also been included as a film resource in scholarly books having to do with sociology or social work, gay marriage, or LGBT families.

The film aired on the Sundance Channel on June 28, 2010, and again on April 25, 2012. It was also included in the Xfinity LGBT History Month programming in October 2017, as a "must-see" documentary.