The former Birmingham City youngster - who has lit up La Liga since departing Borussia Dortmund - was given the green light to line up in his usual central position at Estadi Olimpic Lluis Companys for the mouthwatering derby.
Bellingham's status for El Clasico was uncertain due to a groin injury, but the England international recovered from his affliction to start behind Rodrygo and Vinicius Junior as Real's most advanced midfielder.
However, Bellingham and Real got off to a disastrous start in Catalonia, as with just six minutes in, Ilkay Gundogan - another La Liga new boy - propelled Barcelona into an early lead.
The visitors' efforts to restore parity before the half-time whistle were futile, but Bellingham once again proved to be Real's saviour, picking out the top corner with a rocket of a strike in the 68th minute.
A share of the spoils was seemingly on the cards as the Clasico entered its dying embers, but with two minutes of injury time on the clock, Bellingham tapped home from close range to steal all three points for Real Madrid in dramatic circumstances.
In doing so, Bellingham wrote a new chapter of Blancos folklore, as the 20-year-old became the first Real Madrid player in the 21st century to score at least twice in their first match against Barcelona.
The midfielder's double at Estadi Olimpic Lluis Companys also moved him onto 10 goals from as many matches in the current La Liga season, following in the footsteps of only five other players to have managed double figures in their first 10 Spanish top-flight games over the past 50 years.
Brazilian legends Ronaldo Nazario and Romario both netted 12 goals in their first 10 La Liga appearances, while Robert Lewandowski and Johan Cruyff came up with 11 in 10 for Barcelona.
Finally, Hans Krankl - who spent three years at Barcelona from 1978 to 1981 - also scored 10 goals in his opening 10 Spanish top-flight outings, and Bellingham also left all-time great Zinedine Zidane in his wake.
Indeed, the Frenchman never managed to hit double figures in a La Liga campaign during his time with Real, managing nine goals in both the 2002-03 and 2005-06 campaigns.
Bellingham's overall tally now reads a staggering 11 goals and three assists in 12 matches for Real Madrid across La Liga and the Champions League, scoring in each of his first three matches in the latter tournament.
The 20-year-old unsurprisingly sits at the top of the La Liga goalscoring charts with his double-figure tally, three more than closest challenger Antoine Griezmann, who has struck seven times for Atletico Madrid.
On the back of his Clasico heroics, Bellingham will now travel to Paris for Monday's Ballon d'Or ceremony, where he is up for the top prize and the young player's Kopa Trophy.
Real's derby success keeps them above Girona on goal difference at the top of the La Liga table, and Ancelotti's side are next in action at home to Rayo Vallecano next Sunday night.