The 47-year-old Democratic senator from Illinois swept to victory over his Republican opponent McCain by building an Electoral College majority of 367 votes to McCain's 168 at the time of filing the story. Meanwhile, McCain has conceded defeat to Obama, telling supporters "the failure is mine." McCain told his election-night rally in his hometown of Phoenix that he had congratulated his opponent in a phone call. He thanked his wife Cindy, children, his mother and friends for their support "during the ups and downs of this campaign".
McCain also thanked controversial running mate Sarah Palin, "one of the best campaigners I have ever seen and an impressive new voice in our party."
Obama climbed over the top at 11 p.m. ET with wins in California, Oregon, Washington and Hawaii. It takes 270 electoral votes to win.
But Obama delivered a crushing defeat earlier in the night by clinching Ohio, Pennsylvania and Virginia, states that were key to McCain's presidential electoral strategy, FOX News reported.
And the Democratic nominee took a commanding lead over his Republican rival with a slew of victories in reliable East Coast and Midwestern territory.
Obama has so far won New York, Massachusetts, New Hampshire, Maryland, Rhode Island, Connecticut, New Jersey, Delaware, Vermont and the District of Columbia.
He also won all four electoral votes in Maine and scored a victory in his home state of Illinois, as well as in Iowa, Wisconsin, Minnesota, Michigan and the southwestern state of New Mexico.
McCain has won Texas and Georgia, as well as Idaho, South Dakota, South Carolina, Mississippi, Utah, Louisiana, Arkansas, North Dakota, Kansas, Wyoming, Alabama, Oklahoma, Tennessee, West Virginia and Kentucky. He won three of Nebraska's five electoral votes.
The Democratic nominee has so far amassed 297 electoral votes to McCain's 145, Pennsylvania, with its 21 electoral votes, was one of the few states that voted Democratic in the 2004 presidential election that McCain was actively pursuing.
But McCain's narrow path to victory was made airtight after he lost Ohio and its 20 electoral votes, and Virginia's 13.
He would have had to score an upset in a major Democratic state to recover, as well as win Florida and a number of other states President Bush won four years ago that Obama is contesting.
Thousands of supporters on Tuesday night filled Chicago's Grant Park, where Obama will hold his election celebration.