Now or Never (Grey's Anatomy)

"Now or Never" is the twenty-fourth episode and the season finale of the fifth season of the American television medical drama Grey's Anatomy, and is the 102nd episode overall. Written by Debora Cahn and directed by Rob Corn, the episode was originally broadcast on the American Broadcasting Company (ABC) in the United States on May 14, 2009.

The episode centers around Cristina Yang (Sandra Oh), Alex Karev (Justin Chambers), George O'Malley (T. R. Knight), and Meredith Grey (Ellen Pompeo), who are anxiously waiting for Izzie Stevens (Katherine Heigl) to wake up after her surgery to treat cancer. Meanwhile, Derek Shepherd (Patrick Dempsey) develops an alternative treatment plan for Izzie. Miranda Bailey (Chandra Wilson) confronts Richard Webber (James Pickens Jr.) and Arizona Robbins (Jessica Capshaw) about the pediatric fellowship program. It also touches on Cristina's relationship with Owen Hunt (Kevin McKidd) as she navigates her feelings. Owen offers George career advice, influencing his decision to join the U.S. Army. Another key storyline involves Meredith and Derek's iconic post-it wedding.

The episode marked the last regular appearance of T. R. Knight as a series regular, who portrayed Dr. George O'Malley. O'Malley gets into a life-threatening accident in the episode and dies in the Season 6 premiere, but Knight reprised his role in Season 17 as part of a dream sequence involving Meredith.

The episode attracted an audience of 17.12 million viewers and garnered a 6.2/17 Nielsen rating/share in the 18–49 demographic upon initial broadcast. It received widespread critical acclaim, with high praise directed towards Heigl's performance.