"Grey's Anatomy," created by Shonda Rhimes, premiered on ABC on March 27, 2005, and has become one of television’s longest-running primetime dramas. Over the years, the series has had an extensive cast, with numerous main and supporting characters coming and going. Here's a list of some of the main cast members and the characters they've portrayed, focusing mainly on earlier seasons to provide an overview: 1. **Ellen Pompeo** as Dr. Meredith Grey – The series' central character from the beginning and a surgeon who starts her journey as an intern. 2. **Sandra Oh** as Dr. Cristina Yang (Seasons 1–10) – Meredith's person and a highly competitive surgical intern, later becoming an attending cardiothoracic surgeon. 3. **Patrick Dempsey** as Dr. Derek Shepherd (Seasons 1–11) – A neurosurgeon known as "McDreamy" and Meredith's love interest and later husband. 4. **Katherine Heigl** as Dr. Izzie Stevens (Seasons 1–6) – A surgical intern with a model past, she forms emotional connections with her patients. 5. **Justin Chambers** as Dr. Alex Karev (Seasons 1–16) – An initially abrasive intern who evolves into a caring pediatric surgeon. 6. **T.R. Knight** as Dr. George O'Malley (Seasons 1–5) – A kind-hearted intern and resident who ultimately meets a tragic end. 7. **Chandra Wilson** as Dr. Miranda Bailey – Initially the resident in charge of the interns, she becomes an attending general surgeon and Chief of Surgery. 8. **James Pickens Jr.** as Dr. Richard Webber – The Chief of Surgery with a complex history connected to Meredith's past. 9. **Isaiah Washington** as Dr. Preston Burke (Seasons 1–3) – A cardiothoracic surgeon and Cristina's mentor and lover. 10. **Kate Walsh** as Dr. Addison Montgomery (Seasons 1–3, recurring afterward) – A neonatal surgeon and Derek's estranged wife. 11. **Eric Dane** as Dr. Mark Sloan (Seasons 2–9) – A plastic surgeon and Derek's best friend, nicknamed "McSteamy." 12. **Sara Ramirez** as Dr. Callie Torres (Seasons 2–12) – An orthopedic surgeon with a strong personality and a complicated love life. 13. **Jessica Capshaw** as Dr. Arizona Robbins (Seasons 5–14) – The head of pediatric surgery and Callie's partner for many seasons. 14. **Jesse Williams** as Dr. Jackson Avery (Seasons 6–17) – An ambitious plastic surgeon, part of the Avery dynasty of surgeons. 15. **Sarah Drew** as Dr. April Kepner (Seasons 6–14) – A trauma surgeon with a strong religious background, complicated relationship with Jackson Avery. 16. **Kevin McKidd** as Dr. Owen Hunt – A trauma surgeon and former military doctor who has served as Chief of Surgery. 17. **Camilla Luddington** as Dr. Jo Wilson – A resident with a troubled past who becomes a successful general surgeon and Alex's love interest. 18. **Caterina Scorsone** as Dr. Amelia Shepherd – Derek's neurosurgeon sister with a history of drug addiction. This list includes the primary cast through various points of the series up to Season 17 and is not exhaustive, as "Grey's Anatomy" often introduces new main characters to sustain the ever-evolving storylines. The ensemble nature of the show means that even characters not mentioned here may have had significant impacts on storylines and the show's development.