Justin Edward Fairfax (born February 17, 1979) is an American lawyer and politician who served as the 41st lieutenant governor of Virginia from 2018 to 2022. A member of the Democratic Party, he is the second African-American elected statewide in Virginia, following Douglas Wilder. In 2019, he faced sexual assault allegations dating to 2000 and 2004, which he denied. In 2021, he was a Democratic candidate for Governor of Virginia. He finished fourth in the Democratic primary with 3.54% of the vote.

Fairfax's ancestors were enslaved to the Lords Fairfax of Cameron (for whom Fairfax County, Virginia is named). His ancestor, Simon Fairfax, was freed by Thomas Fairfax, 9th Lord Fairfax of Cameron, who manumitted his slaves as part of his Swedenborgian beliefs. Justin Fairfax was presented with a copy of the manumission document by his father on the day he was sworn in as Virginia's lieutenant governor in 2018. Fairfax's eldest brother, Roger Jr., is a legal scholar.

Fairfax moved with his family from Pittsburgh to Northeast Washington, D.C., when he was five years old. One of four children, Fairfax graduated from DeMatha Catholic High School in Hyattsville, Maryland, where he was senior class president. Fairfax then graduated from Duke University in 2000, with a degree in public policy. After serving on the staff of the Senate Judiciary Committee for two years, Fairfax earned a J.D. degree from Columbia Law School, where he was a member of the Columbia Law Review.

He was a briefing coordinator for Tipper Gore during the 2000 presidential campaign of Al Gore, in the campaign's Nashville, Tennessee office. Fairfax was also a staffer for Democratic senator John Edwards of North Carolina, in his Washington office.

Over the summer of 2004, he joined the John Kerry presidential campaign, as a body man for Edwards, then the vice presidential candidate.

He then served as law clerk to Judge Gerald Bruce Lee of the U.S. District Court for the Eastern District of Virginia in 2005. He worked in the Washington office of the law firm WilmerHale before joining the U.S. Attorney's Office for the Eastern District of Virginia in 2010. Fairfax worked for two years as a federal prosecutor in Alexandria, Virginia. He served as deputy coordinator of the Northern Virginia Human Trafficking Task Force during this time.

Fairfax ran for public office for the first time in 2013, seeking the Democratic nomination for state attorney general. He lost to Mark Herring, but surprised party insiders with his strong performance in the primary. Herring defeated Fairfax by about 4,500 votes out of 141,600 cast in a closer-than-expected race. The Washington Post praised both candidates during the primary, but endorsed Fairfax, writing that he had displayed "an agile and impressive command of the issues with a prosecutor's passion for justice."

After the race, Fairfax co-chaired the 2014 reelection campaign of U.S. Senator Mark Warner from Virginia. The following year, he was recruited to work at the law firm of Venable LLP, in the firm's Tysons, Virginia office. Fairfax then worked for Morrison & Foerster, a law firm where he made partner in September 2018. In July 2019, following sexual assault allegations against him, Fairfax announced that he was resigning from Morrison & Foerster, which had accepted his resignation.