Joseph Patrick Riley Jr. (born January 19, 1943) is an American politician who served as the 60th mayor of Charleston, South Carolina from 1975 to 2016. A member of the Democratic Party, he also served in the South Carolina House of Representatives from 1968 to 1974 and was the 44th President of the United States Conference of Mayors from 1986 to 1987. Riley's 40 years as mayor were the longest in South Carolina history at the time of his retirement and are the longest in Charleston's history.

Riley was born in Charleston, South Carolina. He graduated from The Citadel in 1964 and the University of South Carolina School of Law in 1967. As a member of the Democratic Party, he served in the South Carolina House of Representatives from 1968 to 1974.

In December 1975, Riley was elected the mayor of Charleston, becoming the second Irish Catholic to hold the position. He served for 10 terms. Riley was elected to his seventh term on November 2, 1999, with 71% of the vote; city councilman Maurice Washington received 29%. Riley won his eighth term as mayor in November 2003 in the city's first nonpartisan election with 57% of the vote against other candidates including Jimmy Bailey (32%) and Kwadjo Campbell (9%).

When the Confederate battle flag was flown above the South Carolina State House, Riley organized a five-day protest walk from Charleston to Columbia to promote its removal. The march began on April 2, 2000, with about 600 marchers; the crowd dropped dramatically during the week, but rebounded to about 400 marchers before a protest held on the statehouse grounds on April 6, 2000. The Confederate flag was removed from the South Carolina State House on July 10, 2015, in the aftermath of the Charleston church shooting.

During Riley's tenure, the city of Charleston annexed vast swathes of land, often parcel by parcel. The most controversial annexation was that of Daniel Island in 1990. Riley's critics for the annexation compared him to Saddam Hussein. The city was able to annex Daniel Island despite the wishes of the Guggenheim Foundation which owned the island by annexing it alongside smaller but more valuable properties which offset the foundation's opposition. Other annexations during Riley's tenure include Cainhoy Plantation, Long Savannah on Bees Ferry Road, and the Neck Area below North Charleston.

Riley's first major project was pushing the redevelopment of the central business district. City Council approved $12,500 for a feasibility study for a redevelopment plan on June 7, 1977. A Washington, D.C. consulting group recommended that the city should build a large hotel, commercial, and conference center, and the largely vacant 5-acre lot bounded by King, Meeting, Hasell, and Market streets was a prime candidate. In mid-1977, developer Theodore Gould made a proposal for a $40 million project to be known as the "Charleston Center." The conceptual plans called for a 14-story building with a 700-car parking garage, and preservationists came out strongly against the plans. On January 25, 1978, the first of several lawsuits was filed in an effort to scale back the massive size of the project. Work began in 1981 after several legal challenges. On May 16, 1983, revised plans were released showing the building as it would eventually appear: eight stories in the center but only four around the perimeter. When Gould was unable to secure financing, the city replaced him with new backers and renamed the project "Charleston Place." The center opened on September 2, 1986. Its final cost was approximately $75 million.

In 1987, Riley supported several projects meant to spur redevelopment, including a visitor center on upper Meeting Street and the Waterfront Park along the Cooper River. Riley had a deal with a landowner allowing the city to purchase the land for Waterfront Park for $2.5 million. The land was estimated to be worth between $3.3 and $3.75 million.

In 1989, Riley served on the selection committee for the Rudy Bruner Award for Urban Excellence.