The Unidentified Aerial Phenomena Task Force (UAPTF) was led by the Department of the Navy, operating under the Office of the Under Secretary of Defense for Intelligence (OUSDI).1
A later account gives a slightly different framing of the same arrangement. According to the Report on the Historical Record of U.S. Government Involvement with Unidentified Anomalous Phenomena (UAP), Volume I, the Department of the Navy was asked to lead the UAPTF under the cognisance of the Office of the Under Secretary of Defense for Intelligence and Security, styled in that report as USD(I&S).2
The two sources describe the same chain of oversight rather than conflicting accounts: one states that the department led the task force, the other that it was asked to take on that role, and both place the arrangement under the same intelligence-and-security office rather than treating it as an independent Navy initiative.