The 2008 Democratic National Convention was a quadrennial presidential nominating convention of the Democratic Party where it adopted its national platform and officially nominated its candidates for president and vice president. The convention was held in Denver, Colorado, from August 25 to 28, 2008, at the Pepsi Center. Senator Barack Obama from Illinois gave his acceptance speech on August 28 at Invesco Field in what the party called an "Open Convention". Denver last hosted the Democratic National Convention in 1908. Obama became the party's first nonwhite nominee, and nominee of African descent, for president. Senator Joe Biden from Delaware was nominated for vice president.

Obama officially received the nomination for president on August 27, when his former opponent, U.S. Senator Hillary Clinton of New York, interrupted the official roll call to move that Obama be selected by acclamation. Biden accepted the nomination for vice president on the same night. Obama accepted his nomination the following night in a speech at Invesco Field before a record-setting crowd of 84,000 people in attendance.

Howard Dean presided over the political party in his capacity as Chair of the Democratic National Convention. From the national committee, Leah D. Daughtry served as chief executive of the Democratic National Convention Committee. Speaker of the House Nancy Pelosi served as permanent chair of the convention. Sharing in her responsibilities in the convention were three co-chairmen: Kansas Governor Kathleen Sebelius, Texas State Senator Leticia R. Van de Putte, and Atlanta Mayor Shirley Franklin.

Choosing to hold the convention the day after the Beijing Olympic Games concluded, the Democratic Party convened in Denver in the last week of August, a week before the Republican National Convention in St. Paul, Minnesota. The decision was made, according to the party, to "maximize momentum for our Democratic ticket in the final months of the Presidential election". Customarily, the party of the incumbent president holds its convention after the opposing party has held theirs.^{[citation needed]}

The Democratic National Committee presented themes for each day of the convention. The August 25 theme was "One Nation". The August 26 theme was "Renewing America's Promise" while its August 27 theme was "Securing America's Future". The August 28 theme highlights Obama's campaign motto, "Change We Can Believe In". Featured speakers crafted their messages to the theme of the day.

With close delegate counts for Barack Obama and Hillary Clinton, there was early speculation of the first brokered convention in decades. Democratic National Committee Chair Howard Dean sought to avoid such a circumstance.

In addition to the possibility of a brokered convention, a dispute over seating delegates from Florida and Michigan led some to compare the year's convention with the 1968 Democratic National Convention, which ended in a divided party and unhappiness over the outcome. This speculation ended when Obama was declared the presumptive nominee on June 3, 2008, and Clinton officially announced later that week that she was suspending her campaign and was fully endorsing Obama.

On February 2, 2007, the Democratic Party published "Call for the 2008 Democratic National Convention," the rules governing the convention. There were 3,409.5 pledged delegates, those committed to vote for a particular candidate, selected by primary voters and caucus participants. There were about 823.5 unpledged delegates, those free to vote for any candidate, colloquially known as "superdelegates", for a total of about 4,233 delegates, requiring 2,117 votes to constitute a majority of the convention. The superdelegates consisted of DNC members, Democratic Congress members and Governors, and other prominent Democrats.