The Office of Management and Budget (OMB) is the largest office within the Executive Office of the President of the United States (EOP). OMB's most prominent function is to produce the President's Budget, but OMB also measures the quality of agency programs, policies, and procedures to see if they comply with the president's policies and coordinates inter-agency policy initiatives. 

The current OMB Director is Mick Mulvaney. The OMB Director reports to the President, Vice President and the White House Chief of Staff. 

The Bureau of the Budget, OMB's predecessor, was established in 1921 as a part of the Department of the Treasury by the Budget and Accounting Act of 1921, which was signed into law by president Warren G. Harding. The Bureau of the Budget was moved to the Executive Office of the President in 1939 and was run by Harold D. Smith during the government's rapid expansion of spending during the Second World War. James L. Sundquist, a staffer at the Bureau of the Budget described the relationship between the President and the Bureau as extremely close and of subsequent Bureau Directors as politicians and not public administrators. 

The Bureau was reorganized into the Office of Management and Budget in 1970 during the Nixon administration. The first OMB included Roy Ash (head), Paul O'Neill (assistant director), Fred Malek (deputy director) and Frank Zarb (associate director) and two dozen others.
To what?
the Office of Management and Budget