Derek Christopher Shepherd, often referred to as "McDreamy" for his "attractiveness", is a fictional surgeon from the ABC medical drama Grey's Anatomy, portrayed by actor Patrick Dempsey. He made his first appearance in the series' pilot episode, "A Hard Day's Night", which was broadcast on March 27, 2005.

Derek was married to Addison Montgomery (Kate Walsh), but their relationship ended in divorce in 2007. Before his death in 2015, Derek was happily married to his longtime partner, Meredith Grey (Ellen Pompeo), with whom he had three children.

Derek served as the Chief of Surgery at Seattle Grace Mercy West Hospital (previously Seattle Grace Hospital, and later Grey Sloan Memorial Hospital). However, he abruptly resigned from the position in Season 7, following the traumatic hospital shooting.

For his portrayal of Derek Shepherd, Dempsey earned widespread recognition. He was nominated for the Golden Globe Award for Best Actor – Television Series Drama in both 2006 and 2007. Additionally, he also received a nomination for the Screen Actors Guild Award for Outstanding Performance by a Male Actor in a Drama Series.

Derek arrives at Seattle Grace Hospital and comes as the new Head of Neurosurgery from New York City. He is a Bowdoin College graduate and attended Columbia University College of Physicians and Surgeons alongside his childhood best friend Mark Sloan and ex-wife Addison Montgomery and Private Practice characters Naomi Bennett and Sam Bennett. Derek was a student of Dr. Richard Webber and was enticed to come with an "offer he couldn't refuse" – the position of Chief of Surgery, which he eventually turned down. He specializes in highly complex tumors and conditions of the brain and spine, and came to Seattle Grace with a reputation for taking on "lost causes" and "impossible" cases that most of his peers would turn down. As an attending, he is both well-liked by patients and his scrub nurses for his compassion and polite bedside manner and feared by interns and residents who are intimidated by his reputation and high standards. He is passionate about his job and has been known to expel staff or remove students (or at least threaten them) from his service for being disrespectful about patients or if he deems their attitude to be detrimental to his patient's well-being.

Derek first meets Meredith Grey at a bar and has a one-night stand with her. He soon finds out that she is an intern at Seattle Grace. They begin to have feelings for one another, and it causes some awkwardness at work particularly after her supervising resident Dr. Miranda Bailey discovers their relationship. While most of his family members accepted Meredith, his sister, Nancy, particularly disliked her and repeatedly called her "the slutty intern"; as of season nine she still refuses to speak to Meredith or acknowledge her as her sister-in-law. His mother Carolyn approved as she felt Meredith's gray perspective of life complemented Derek's tendency to see everything in black and white.

Derek's background was generally a mystery for the first season and source of speculation amongst his colleagues due to his sudden departure from an established and highly respected practice in New York. In the season one finale, his past eventually catches up with him when his estranged wife Addison moves to Seattle and is offered a position by Dr. Webber. Shortly after that, his childhood best friend Mark joins Seattle Grace as the new head of plastic surgery. Derek and Addison attempt to repair their marriage but attempts were futile. Addison and Derek each began their practice in New York City, which placed a strain on their marriage. Their marriage was troubled in the years leading to Derek's decision to leave New York as it is eventually revealed in both Grey's Anatomy and Private Practice that Derek's mother did not approve of her (choosing to give her dead husband's ring to Derek's second wife, Meredith Grey) and Addison's brother Archer disliked Derek. Addison's affair with Derek's best friend Mark Sloan drove the wedge even further and Derek's departure to Seattle. Addison briefly attempted to have a relationship with Mark, which resulted in her becoming pregnant. She then had an abortion soon after she discovered that Mark cheated on her, and as she was still in love with Derek. She then moved to Seattle. In the season eight episode "If/Then", Meredith dreams of an alternate universe where her mother never had Alzheimer's; Derek and Addison are still married, but their strained relationship and Shepherd's disillusionment causes his career to stagnate, earning him the nicknames "Bad Shepherd" and "McDreary".

When Derek is offered the Chief of Surgery position for the second time, he persuades the board to keep Dr. Webber on the staff. During the merger of Seattle Grace with Mercy West their relationship sours when Derek disagreed with Richard's handling of the merger and Richard begins to display uncharacteristic behavior. Derek learns from Meredith that Richard has since resumed drinking and feels forced to have him removed as Chief of Surgery. With mixed feelings, Derek offers him an ultimatum: go into rehab and pick up where he left off after, or retire from the hospital altogether.