One Tree Hill is an American drama television series created by Mark Schwahn, which premiered on September 23, 2003, on The WB. After the series' third season, The WB merged with UPN to form The CW, and from September 27, 2006, the series was broadcast by The CW in the United States until the end of its run on April 4, 2012. The show is set in the fictional town of Tree Hill, North Carolina, and initially follows the lives of two half-brothers, Lucas (Chad Michael Murray) and Nathan Scott (James Lafferty), who compete for positions on their school's basketball team and the drama that ensues from the brothers' romance.

Most of the filming took place in and around Wilmington, North Carolina. Many of the scenes were shot near the battleship USS North Carolina and on the University of North Carolina Wilmington campus. The first four seasons of the show focus on the main characters' lives through their high school years. Within these seasons, we see the characters build unexpected relationships as they face the challenges of growing up in a small town. However, at the beginning of the fifth season, Schwahn advanced the timeline by four years to show their lives after college. This season featured a new storyline supported by flashbacks to their college years. Later, Schwahn made it jump a further fourteen months from the end of the sixth to the start of the seventh season. The opening credits were originally accompanied by the song "I Don't Want to Be" by Gavin DeGraw. The theme was removed from the opening in the fifth season; Schwahn said that this was to lower production costs, to add more time for the storyline, and because he felt that the song was more representative of the core characters' adolescent past than their present maturity. The opening then consisted only of the title against a black background. The theme was restored for season 8, in response to audience demand, and was sung by a different artist each episode.

The series premiered to 2.5 million viewers and rose to 3.3 million in its second week, becoming one of only three shows to rise in their second episode during the 2003–2004 television season. The series received numerous award nominations, winning two Teen Choice Awards.

On May 12, 2009, it was confirmed that Murray and Hilarie Burton (Peyton) had declined to return for the seventh season, although accounts of what transpired vary. Their characters (Lucas and Peyton) had been two of the five main protagonists, and had provided one of its central love stories, throughout the show. On May 17, 2011, The CW renewed One Tree Hill for a ninth and final season, placing an order for 13 episodes. Bethany Joy Lenz (Haley) and Sophia Bush (Brooke) were signed as full-time regulars for one final season, and Lafferty appeared as a part-time regular. Murray returned for a special appearance during the final season, which premiered on January 11, 2012. The show is the fourth-longest-running series on The CW network, or the networks that came together to make it up (The WB and UPN), after Supernatural, 7th Heaven and Smallville.

In August 2024, it was reported that a revival of the series was in development, with Bush and Burton returning while conversations with other cast members were ongoing.