James Wilson is the oncology department head and House's close friend in House M.D.
Wilson works at Princeton-Plainsboro Teaching Hospital and often acts as House’s informal adviser, conscience, and emergency contact. His medical specialty gives him a different perspective from House’s diagnostic team: Wilson focuses on cancer treatment and on the emotional realities faced by patients and families.
The friendship between Wilson and House is one of the show’s defining relationships. Wilson frequently criticizes House’s recklessness, yet he repeatedly helps him through professional, legal, and personal crises. Their bond is deliberately comparable to the relationship between Dr. John Watson and Sherlock Holmes, an important influence on the series.
Wilson is played by Robert Sean Leonard. The character’s later storyline includes a diagnosis of thymoma, a tumor associated with the thymus. That plot drives the final season and helps explain why the series finale centers so strongly on House’s willingness to sacrifice his own future for his friend.