The 2004 D.C. United season was the eighth season of the club's existence. It was highlighted by winning their first MLS Cup championship since 1999.
The season was hallmarked by United winning their fourth Major League Soccer championship, winning MLS Cup 2004 3–2 over Kansas City Wizards. To date, this was the last time in franchise history that the team has won an MLS Cup title. Additionally, by winning the championship, some cite that it marked a "second golden age" in United, as the United matched their late 90s dynasty by doubling their trophy case. Following the 2004 title, United would go on to win two MLS Supporters' Shields, to claim the most in the league, as well as their second U.S. Open Cup title.
In terms of player and manager transactions, the offseason saw English head coach Ray Hudson end his two-season stint with the club, as United management fired him out of dissatisfaction with his results as a manager. Early in January, United signed retired MLS star Piotr Nowak to the helm of head coaching duties. The hiring of Nowak was unprecedented at the time, as no other head coach was a former MLS player in league history. However, the signing of Nowak marked a new trend of first generation MLS players assuming coaching duties for second generation MLS players.
United made national, and international, headlines this year by drafting then 14-year-old prospect Freddy Adu as the first pick of the MLS SuperDraft. Although United did not have worst record in 2003, and in fact, made the playoffs, MLS orchestrated a series of negotiations between United and Dallas Burn, who originally had the first overall selection. Since Adu signed with the league, per Adu's request, the league led a series of agreements between the two sides to give Dallas additional allocation from United so that Adu could play for his local club, as he grew up near Potomac, Maryland.