Beverly "Bev" Marsh is a fictional character created by Stephen King and one of the main characters of his 1986 horror novel It. The character is seen as a member of "The Losers Club" and a romantic interest of fellow members Bill Denbrough and Ben Hanscom.

She is portrayed in the 1990 TV miniseries adaptation by Emily Perkins as the young version and Annette O'Toole as an adult. In the film adaptions of 2017 and the 2019 sequel, Sophia Lillis and Jessica Chastain portray Beverly Marsh as the younger and adult version, respectively.

Beverly Marsh was born in 1947. She is the daughter of Alvin and Elfrida Marsh. Her mother's presence in her life differs among the three continuities.

Beverly is a classmate of Ben Hanscom, who harbors a secret crush on her. Ben writes her an anonymous love poem which states, "your hair is winter fire, January embers, my heart burns there too." Beverly is led to believe that the poem was written by Bill Denbrough, who grows up to be a professional writer.

Beverly eventually joins "The Losers Club" and befriends Eddie Kaspbrak, Richie Tozier, Mike Hanlon and Stanley Uris. Beverly has her first encounter with Pennywise in her bathroom when she hears voices coming from her sink chanting "We All Float Down Here". A balloon-like construct begins growing from her sink and bursts, covering her bathroom with blood. Beverly's screams attract the attention of her father, who cannot see the blood. She confides in The Losers Club, who can all see the blood and help her clean the bathroom.

The Losers Club eventually are chased into the sewers by Henry Bowers under the influence of Pennywise. After the group finds and finishes off the clown, they find themselves lost. After they escape the sewers, the Losers make an blood oath that if Pennywise hasn't been defeated, they will all return to Derry to finish him.

In her adulthood, due to the power of Pennywise and the town of Derry, Beverly forgets about The Losers Club and her childhood. She becomes a fashion designer and enters an abusive relationship with her husband, Tom Rogan. After she gets a call from Mike asking her to return to Derry, she stands up to Tom and finally leaves the relationship. She returns to Derry and reunites with The Losers Club. Beverly returns to her old home, now inhabited by an old woman named Mrs. Kersh, who informs her that her father has been deceased for five years. She apologises and begins to leave, only to be invited in by Mrs. Kersh for tea. However, Mrs. Kersh is revealed to be a form of Pennywise and Beverly escapes. She reunites with Ben, and shares a romantic encounter with him, but Ben realises that Beverly is another form of Pennywise. The Losers Club return to the sewers to face Pennywise for the final time. Unfortunately, the confrontation results in Eddie's death, but the Losers are able to overcome and kill Pennywise. After the confrontation, Ben is finally able to confess his feelings for Beverly, and they begin a relationship.

Beverly is portrayed in the 1990 TV miniseries by Emily Perkins as a child and Annette O'Toole as an adult. This interpretation remains fairly faithful to the novel. Perkins' portrayal of Beverly was met with a relatively positive reception, but O'Toole's portrayal was met with a more negative one.