The 24-time major champion defeated Lorenzo Musetti 6-4 6-2 to ensure he would walk away from Roland-Garros with a medal.
Djokovic will now face number two seed Carlos Alcaraz in a rematch of last month's Wimbledon final.
The 37-year-old was aware of the enormity of the achievement in going one step further, having suffered semi-final losses to Rafael Nadal, Andy Murray and Alexander Zverev in three previous Olympic semi-finals, though he did claim bronze at the Beijing Games in 2008.
"I have been waiting for this for almost 20 years," Djokovic said in his on-court interview.
"I've played four Olympic Games, this is my fifth and '’ve never passed the semi-finals. I lost three semi-finals in my first four Olympic Games.
"I managed to overcome this big hurdle. I must be honest and say that I was thinking about all the semi-finals that I lost."
The Serbian had to overcome injury concerns after his quarter-final match against Stefanos Tsitsipas, and Djokovic was more encouraged by his mental strength against an opponent that has made great strides on the ATP Tour this season in Musetti.
"I just tried to be in the present moment. I played against a player who is in great form and really came out firing from both ends," Djokovic added.
"I just tried to maintain the focus and do what I have to do."
Sunday's final between Djokovic and Alcaraz will be the seventh meeting between the pair, with the head-to-head currently at three apiece.
The Italian was pushed all the way, but held strong to prevail 7-5 7-5 in just over two hours at Roland-Garros.
Zverev knew he was in for a tough day from the start, losing his serve in the opening game, and though he managed to claw back to draw 5-5, Musetti got another vital break to take the first set.
The pair matched each other throughout the second, but Musetti eventually found his edge with a three-game winning run when it mattered and wrapped up the match by serving to love.
He will face either former world number one Novak Djokovic or Greece's Stefanos Tsitsipas in the next round.
Data Debrief: Musetti comes out on top
It was just the second-ever meeting between Musetti and Zverev, with the first coming to an early end when he had to retire through injury in Madrid in 2022.
He put that right today though, and becomes just the third Italian player to reach the men's singles semi-finals at the Olympics in history after Uberto De Morpurgo (Paris 1924) and Paolo Cane (Los Angeles 1984).
Musetti, who was beaten by Novak Djokovic in the semi-finals, prevailed 6-4 1-6 6-3 on Saturday at Roland-Garros.
It marked a historic success for Italy, bringing up the nation's first tennis player to win a medal at the Olympics since Uberto de Morpugo in 1924, with those Games having also taken place in Paris.
While Auger-Aliassime leaves empty-handed from the singles, he did win bronze in the mixed doubles.
Prior to Musetti's triumph, Tommy Paul and Taylor Fritz won in straight sets to claim the bronze medal in the men's doubles, beating Tomas Machac and Adam Pavlasek.
After falling to defeat to eventual gold medallists Matthew Ebden and John Peers in the semi-finals, the American duo dusted themselves down to claim a 6-3 6-4 victory.
Paul and Fritz controlled the opening set, earning a double break in the sixth game and, despite losing the next two, held on to take the early advantage.
The Americans squandered three match points to seal the win, but confirmed their place on the podium in the 10th game, with Team USA taking home two medals from the doubles after Austin Krajicek and Rajeev Ram's silver earlier in the day.
It was not all doom and gloom for Czechia, though, with Machac and Katerina Siniakova having claimed gold in the mixed doubles on Friday.
