Susan Coyne is a Canadian writer and actress, best known as one of the co-creators and co-stars of the award-winning Slings and Arrows, a TV series which ran 2003–06 about a Canadian Shakespearean theatre company. In 2006, she won two Gemini Awards for her work on the show, one for best performance in a supporting role and one for best writing for a dramatic series (shared with her fellow co-creators, Bob Martin and Mark McKinney). In 2007, she again won for writing, but lost to co-star Martha Burns in the acting category. She has been nominated for four Writers Guild of Canada awards, in 2006 and 2007 and 2015, and won three.

She wrote the screenplay for the 2017 film,The Man Who Invented Christmas, starring Dan Stevens and Christopher Plummer. Other television writing credits include Mozart in the Jungle, The Best Laid Plans, and L.M. Montgomery's Anne of Green Gables.

A veteran of the Toronto theatre scene, she acted for several seasons at the Stratford Festival, was one of the founding members of the Soulpepper Theatre Company and is currently a playwright-in-residence at the Tarragon Theatre. Her two best-known plays are Kingfisher Days, an adaptation of her critically acclaimed memoir of the same name, and Alice's Affair. The edition of this memoir that was published in America was titled In the Kingdom of Fairies. It recounts her experiences in the summer of 1963 at her family's summer cottage on Lake of the Woods. She is also known for her translations of Anton Chekhov. Coyne also appeared in the Fernando Meirelles adaptation of the Jose Saramago novel, Blindness.

Coyne comes from a prominent Canadian family: she is the daughter of James Coyne, a former governor of the Bank of Canada, the sister of journalist Andrew Coyne and the cousin of constitutional lawyer Deborah Coyne. She attended the St. John's-Ravenscourt School in Winnipeg, as did her acting colleague Martha Burns. In 2017 she was appointed a Member of the Order of Canada by the Governor General for her contributions to Canadian theatre, film and television as an actor and writer. She is a graduate of the National Theatre School of Canada and was married to Canadian actor/director Albert Schultz. They have two children.