The 1951 Philadelphia municipal election, held on Tuesday, November 6, was the first election under the city's new charter, which had been approved by the voters in April, and the first Democratic victory in the city in more than a half-century. The positions contested were those of mayor and district attorney, and all seventeen city council seats. There was also a referendum on whether to consolidate the city and county governments. Citywide, the Democrats took majorities of over 100,000 votes, breaking a 67-year Republican hold on city government. Joseph S. Clark Jr. and Richardson Dilworth, two of the main movers for the charter reform, were elected mayor and district attorney, respectively. Led by local party chairman James A. Finnegan, the Democrats also took fourteen of seventeen city council seats, and all of the citywide offices on the ballot. A referendum on city-county consolidation passed by a wide margin. The election marked the beginning of Democratic dominance of Philadelphia city politics, which continues today.

Joseph Sill Clark Jr. was an American writer, lawyer and politician. A member of the Democratic Party, he served as the 90th Mayor of Philadelphia from 1952 to 1956 and as a United States Senator from Pennsylvania from 1957 to 1969. Clark was the only Unitarian Universalist elected to a major office in Pennsylvania in the modern era.