Burris, 73, did no active campaigning during his few weeks as a candidate. When he entered the race, he issued a short press release instead of holding an event, and he left the same way, the Chicago Sun-Times reported Saturday.
"I want to thank all of those who backed me for the office of mayor and those who signed the petition, but I will not be offering myself as a candidate for mayor of Chicago," he said. "In the last 30 years, the people of Chicago have not had many opportunities to elect a new mayor -- specifically, for an open seat. This election is very important, because it will determine whether Chicago remains the attractive, competitive, creative, effective, and productive city we all know it to be."
The Democratic field remains a crowded one, headed by former Rep. Rahm Emanuel, a former Illinois congressman who recently resigned as President Obama's chief of staff.
Burris was the first black politician to win statewide office in Illinois, serving as comptroller and attorney general. But he has not won an election since 1995.
He was appointed to fill Obama's unexpired Senate term by disgraced former Gov. Rod Blagojevich.