After 104 hands of heads-up action dominated almost entirely by the 22-year-old Dane, Eastgate turned the wheel straight to counter his Russian adversary's two pair and clinch the title, claiming his first World Series of Poker bracelet and a first prize totaling $9,152,416.
In the process he became the youngest-ever WSOP Main Event winner.
After the November Nine were reduced to the November Two over more than 14 hours of play on Sunday, Demidov and Eastgate returned to the Rio's Penn and Teller Theater at 10 p.m. on Monday evening to finish the job, battling it out in front of a raucous crowd of hundreds of poker fans who jammed the auditorium to witness the event.
After a short presentation to honor 2008 WSOP Player of the Year Erick Lindgren, during which the E-Dog was presented with a custom Harley-Davidson for his accomplishments - and took the opportunity to invite tonight's winner to his home game immediately following the final table - boxing announcer Michael Buffer exhorted the dealer to "Let's get ready to shuffle" and the action resumed shortly before 11 p.m.
Read our live updates from the final table here.
Eastgate came into the heads-up match with an $80,300,000 to $56,600,000 advantage, but Demidov quickly set about reversing the trend, winning a number of big pots in the first hour of play to take over the chip lead.
That seemed to light a fire under Eastgate, who battled back to regain his advantage and then pressed the issue, winning a pair of juicy pots against Demidov when he caught his rival bluffing the river with ace-high, the second time after turning a diamond flush and convincing Demidov to commit $12 million on fifth street.
That pot gave the Dane an advantage of almost $100 million, and seven hands later Eastgate had clinched the victory.
In the climactic hand, Eastgate limped from the button and Demidov checked his option in the big blind. The flop came K♠ 3♥ 2♦ and Demidov checked to Eastgate, who bet out $1.25 million. Demidov made the call and the turn was the 4♣.
Again, Demidov checked and again Eastgate fired, making it $2 million to play. This time, Demidov sprung the check-raise and slid another $4 million across the felt.
Eastgate smooth-called and after the 7♠ fell on the river, Demidov quickly shoved all-in. Eastgate called just as quickly, his A♦ 5♠ trumping his adversary's 4♥ 2♥ to win the day for Denmark and ship the bracelet to Peter the Great.
For his second-place finish, Ivan Demidov takes $5,809,595, a nice complement to the £344,850 he earned for his third-place finish in the Main Event of this year's World Series of Poker Europe.
PokerListings.com was on the scene at the final table and our coverage is unmatched. We have a full recap with Paula Elle on PokerListings TV as well as an exclusive interview with the champion and a written recap of the Main Event's final day. Check out the 2008 WSOP section for details.