Nelson Diaz (born 1948) is a United States lawyer who has been a Philadelphia city solicitor, a judge on the Philadelphia Court of Common Pleas, and General Counsel at the United States Department of Housing and Urban Development (HUD). He was mentioned as a possible HUD Secretary in the Obama Administration, before Obama announced that Shaun Donovan was his pick for the position. He ran unsuccessfully for the Democratic nomination for Mayor of Philadelphia, Pennsylvania in the 2015 election.