In House M.D., James Wilson is the oncologist who works alongside Gregory House.
Wilson is the head of the Department of Oncology at Princeton-Plainsboro Teaching Hospital. His medical specialty gives him a different perspective from House's diagnostic work, and he often helps interpret difficult cases or challenge House's assumptions.
The character is also House's closest friend, but this question concerns Wilson's professional role rather than their friendship. Robert Sean Leonard played Wilson for the full run of the series. Wilson's calm, empathetic manner frequently contrasts with House's confrontational style.
Wilson's personal story includes several marriages, family conflicts, and a serious illness late in the series. His relationship with House remains one of the show's central emotional threads, while oncology repeatedly connects him to patients facing life-threatening disease.