Douglas Arthur Sims II is a United States Army lieutenant general who has served as director of the Joint Staff since January 2024. He most recently served as the director of operations of the Joint Staff from 2022 to 2024. He served as commanding general of the 1st Infantry Division and Fort Riley from 2020 to 2022, and prior to that served as deputy director for Regional Operations and Force Management of the Joint Staff from 2018 to 2020.

The director of the Joint Staff (DJS) is a three-star officer who assists the Joint Chiefs of Staff, a cabinet of senior military officers within the United States Armed Forces who advise the secretary of defense and the president on military matters. The director assists the chairman of the Joint Chiefs of Staff in managing the Joint Staff and with the management and organization of the staff's members. The director also chairs meetings of the Operations Deputies, a subsidiary body comprising the director and a three-star delegate from each service who preview or resolve issues before they are escalated to the four-star level of the Joint Chiefs of Staff.