Joseph diGenova (born February 22, 1945) is an American lawyer and political commentator who served as the United States Attorney for the District of Columbia from 1983 to 1988. He and his wife, Victoria Toensing, are partners in the Washington, D.C., law firm diGenova and Toensing. He is known for promoting conspiracy theories about the Department of Justice and the FBI. He and Toensing frequently appeared on Fox News and Fox Business channels, until diGenova used a November 2019 appearance to spread conspiracy theories about George Soros, leading to widespread calls for him to be banned from the network.

In March 2018, President Donald Trump announced that diGenova and Toensing would join his legal defense team during the Mueller investigation; the appointments were withdrawn days later, citing an unspecified conflict of interest, though Trump personal attorney Jay Sekulow said they might assist in other legal matters. In July 2019, diGenova and Toensing began representing Ukrainian oligarch Dmitry Firtash to assist his efforts to avoid extradition to the United States under a federal indictment, as their associate and Trump's personal attorney Rudy Giuliani sought information in Ukraine to damage Democratic presidential candidate Joe Biden. In November 2020, Trump named diGenova, Toensing, Sidney Powell and Jenna Ellis to join a legal team led by Giuliani to overturn the results of the 2020 presidential election in which Trump was defeated.

In April 2026, diGenova was selected by the Department of Justice to lead an inquiry "into whether former federal officials committed crimes in investigating President Trump".

DiGenova was an aide to Republican Senator Charles Mathias of Maryland, eventually serving as Mathias' legislative director. After Republicans won the U.S. Senate in the 1980 elections, diGenova was named chief counsel and staff director of the Senate Rules Committee and counsel to the Senate Judiciary, Governmental Affairs, and Select Intelligence committees.

As a U.S. attorney, diGenova led the prosecution of Jonathan Pollard, who pleaded guilty in 1987 to spying for Israel.

He also led investigations into corruption in the administration of Washington, D.C., Mayor Marion Barry that led to convictions of 12 officials, including two deputy mayors.

DiGenova later served as Independent Counsel investigating the 1992 preelection search of then-candidate Bill Clinton's passport file by officials of the George H. W. Bush administration. DiGenova concluded that the passport search had been "stupid, dumb and partisan," but not illegal, and that the government should apologize to the officials who ordered the search.

DiGenova and his wife, Victoria Toensing, started their Washington law firm, diGenova & Toensing, in January 1996.