"It's the person who controls access to the president and controls his schedule ... and decides what information reaches the president.
Emanuel, a former adviser to ex-president Bill Clinton, will be a key figure in supporting the country's first African-American leader when he formally takes office on January 20, during the world's worst financial crisis in a century and with the unpopular wars in Afghanistan and Iraq on his hands.
A day after triggering a political earthquake not seen since Ronald Reagan's 1980 landslide, Obama also named key figures of the transition team which will spend the next 76 days preparing for his inauguration and taking up of the US presidency.
Rob Reynolds said Obama will also be attending a meeting of the G20 group of nations being convened by George Bush, the current US president, at the White House on November 15 to try and address the ongoing global economic turmoil.
Bush earlier praised what he called "an impressive victory" against Obama's rival, Republican John McCain.
He said: "I had a warm conversation with president-elect Barack Obama. I congratulated him and Senator [Joe] Biden on their impressive victory.
"I told the president-elect he can count on complete co-operation from my administration as he makes the transition to the White House."
Condoleezza Rice, the US secretary of state, said Obama's election was "an extraordinary step forward".
She said: "As an African-American, I'm especially proud. America has been through a long journey, making race not a factor in our lives."
Millions of people around the world continued celebrating Obama's historic victory on Wednesday.
Outside of the White House in Washington DC in the early hours of Wednesday, thousands of people crowded the streets , chanting "goodbye!" and "pack your sh*t!" in anger at the unpopular administration of president Bush as well as hailing Obama with cries of "yes we can!" and "yes we did!".
In his victory speech at Chicago's Grant Park the previous night, Obama told tens of thousands of supporters: "Change has come to America".
"If there's anyone out there who still doubts that America is a place where all things are possible, tonight is your answer," he said.
With results given in 48 states and Washington DC, Obama had swept past the 270 electoral college votes needed for victory, taking 349 to McCain's 162.
Rob Reynolds, reporting from Chicago, said the election was a "decisive victory".
"It is truly a national victory with a national mandate for change," he said.
Obama's race for the White House began to turn decisively in his favour after he won the key battleground state of Ohio. The result was a blow to McCain, as no Republican candidate has managed to gain the presidency without winning the state.
The Democratic candidate's victory marked the pinnacle of four centuries of striving for equal rights for African-Americans in the country.
Jesse Jackson Jr, the Obama campaign co-chair, said: "Barack Obama as the 44th president ... it is mind-boggling, mind-blowing.
"Our children walk into a very different America tomorrow," he told Al Jazeera.
"For some people it is the end of a two-year campaign and for others it has been a 200-year trek ... The civil rights movements, among others, have made this moment possible."