Shakespears Sister are an alternative pop and rock musical duo that was formed in 1988 by Irish singer-songwriter Siobhan Fahey, a former member of Bananarama. Shakespears Sister was initially a solo act but became a duo by 1989 with the addition of American musician Marcella Detroit. Together they released two top-ten albums and a string of top-forty hits, including the 1992 single "Stay", which remained at No. 1 on the UK Singles Chart for eight weeks. Detroit was let go from the band in 1993, leaving Fahey as the sole member again, until the latter ended the project in 1996. After working under her own name for some years, Fahey revived the Shakespears Sister moniker in 2009. In 2019, Fahey and Detroit reunited as Shakespears Sister for a tour and released the singles "All the Queen's Horses" and "When She Finds You", and the EP Ride Again.

Shakespears Sister was conceived as a solo project by Siobhan Fahey, a one-time punk turned chart-pop singer who had left the successful British/Irish girl-group Bananarama in 1988, due to disillusionment with the group's musical direction. The name was adapted from the title of the song "Shakespeare's Sister" by The Smiths, which was in turn a reference to Virginia Woolf's work A Room of One's Own. According to Fahey, the misspelling began with an accidental punctuation slip on a woodcut sign (the missing apostrophe from Shakespeare's). She decided to keep it because "It made it sort of my thing, as opposed to the song by The Smiths". Fahey has described the meaning of the name being "Siobhan Fahey is the mother, the sister, the daughter, it's not the artist. The artist is Shakespears Sister."

Fahey began writing and recording work for the project with their record producer Richard Feldman. Several other musicians were involved in the songwriting, one of whom was Feldman's friend and colleague Marcy Levy, a veteran of live and studio work with Eric Clapton (with whom she had written "Lay Down Sally"), Leon Russell and Bob Seger as well as a songwriter for artists including Jennifer Rush, Chaka Khan and Patty Weaver. An accomplished singer and multi-instrumentalist (guitar, harmonica and keyboards), Levy also made vocal and instrumental contributions to the sessions, staying on as a prominent 'hired hand'. During this time, Fahey suggested that Levy — who had previously failed to get a couple of solo albums released - take on a new professional name in order to gain a new lease of artistic life. Levy agreed and restyled herself as Marcella Detroit, a name she has used throughout her time with Shakespears Sister and afterwards.

The debut Shakespears Sister single was "Break My Heart (You Really)/Heroine" (released as a double A-side in the UK and as two separate singles in the United States, although none of the releases charted successfully). "Break My Heart" had been intended to differentiate Fahey's solo artist persona from her past work with Bananarama. David A. Stewart (Fahey's then-husband and a member of Eurythmics) had been impressed by the musical chemistry between Fahey and Detroit in the recording studio. Seeing potential benefit in turning Shakespears Sister from a solo project into a band, he suggested that Fahey and Detroit should unite as a duo. It was a suggestion that was backed by Feldman, Fahey's management, and her record company, London Records. Despite initial reluctance from both women (both of whom wished to retain their independence and avoid band commitments), Detroit was invited to become "a 50% member" towards the end of the recording sessions. She would later recall "by the time we did the last song on the first album, my role became more integral... I didn't just want to be a background singer... It was Siobhan's band, this was made perfectly clear. But I was cool with that – that's the way it was."

The second Shakespears Sister single, "You're History", gave the project its breakthrough hit. The song displayed the effectiveness of the vocal pairing of Fahey and Detroit, setting the former's sly, murmuring contralto against the latter's R&B-influenced soprano and falsetto parts. It also features a solo from guitarist Stevie Salas. "You're History" reached the top 10 on the UK Singles Chart in the summer of 1989, as did the debut Shakespears Sister album, Sacred Heart, which was certified Gold by the BPI. Two further singles were released from the album, "Run Silent" and "Dirty Mind", though both failed to peak within the Top 50 of the UK chart.

In September 1991, Shakespears Sister released a new single, "Goodbye Cruel World", which peaked at No. 59. The next single, "Stay", marked Shakespears Sister's first and only No. 1. It remained at the top of the UK Singles Chart for eight full weeks, achieved similar success on international charts, and won Best British Video at the 1993 BRIT Awards. Notably the song foregrounded Detroit, who sang the majority of the lead vocals and featured prominently in the video. This allegedly led to tension with Fahey; Detroit later claimed that Fahey felt sidelined as the project's instigator and usual lead vocalist, didn't consider the song to be representative of the band, and had opposed its release as a single.

Hormonally Yours was released the following month. The album sold well on the strength of "Stay", eventually being certified double platinum by the BPI. The duo continued to enjoy success with further singles from Hormonally Yours: "I Don't Care" peaked at No. 7, "Hello (Turn Your Radio On)" at No. 14, and a re-release of "Goodbye Cruel World" at No. 32. During 1992, however, tensions between Fahey and Detroit became overt, with backstage infighting and arguments marring the band's tour. A fifth single, "My 16th Apology", was released in early 1993, reaching No. 61.

Although Fahey and Detroit seemed at first to have resolved their differences, Fahey was struggling with personal issues. That led to the cancellation of what would have been the band's highest-profile concert, at the Royal Albert Hall, and Fahey's temporary hospitalization for depression. The duo decided to put Shakespears Sister on hiatus, and Detroit began working on a solo album (something which had already been agreed and scheduled around band work). During this time Fahey decided to end her partnership with Detroit but chose not to discuss this with her directly. Instead, Detroit was publicly dismissed at the 1993 Ivor Novello Awards ceremony, at which Hormonally Yours won Best Contemporary Collection of Songs (and which Detroit attended, although Fahey did not). Fahey's acceptance speech, delivered by her publisher, contained a farewell to Detroit wishing her "all the best for the future, all's well that ends well."