The victory puts Djokovic, a two-time champion at Roland-Garros, within touching distance of winning a men’s record 23rd grand slam title.
The match was evenly poised at 1-1 in the third set when Alcaraz appeared to experience cramp and began to struggle with his movement.
His condition improved in the fourth set after receiving treatment, but by now Djokovic clearly had the upper hand as he raced to victory, setting up a final against last year’s runner-up Casper Ruud after the Norwegian comfortably beat Germany’s Alexander Zverev 6-3 6-4 6-0.
“First and foremost, I have to say tough luck for Carlos,” Djokovic said in his on-court interview. “At this level, the last thing you want is cramps and physical problems in the late stages of a grand slam. I hope he can recover and come back very soon.”
Friday’s first semifinal was the contest most had been anticipating in the men’s competition, pitting the most decorated player in the draw against the current world No. 1.
Djokovic took the opening set as Alcaraz, who failed to convert any of his four break points, was unable to find rhythm or consistency in windy conditions on Court Philippe-Chatrier.
By contrast, Djokovic was accurate and unrelenting, heaping pressure on a player 16 years his junior.
The Spaniard stepped up his level in the second set and had the crowd in raptures when he raced to the back of the court and – almost impossibly – fired a forehand past Djokovic while facing the wrong way.
Alcaraz got his first break of the match at 4-3 when Djokovic sent a backhand long, but the Serbian hit back straight away with a break of his own.
With the match gaining intensity, Alcaraz engineered three set points at 5-4 before Djokovic responded superbly by winning the next five points in a row to ensure the set remained tied.
The same scenario occurred at 6-5 but this time Alcaraz made no mistake, converting the first of another three set points.
However, things quickly unraveled for the 20-year-old. Much to the displeasure of the crowd, he had to forfeit a service game at the start of the third set as cramps started to limit his movement.
Struggling physically, Alcaraz changed tactics and upped his shot power in an effort to shorten the points.
Although it looked at times like he could find a way back into the match, Djokovic never wavered and wrapped up the victory in three hours and 23 minutes.
He ended the contest with 39 winners and 36 unforced errors to Alcaraz’s 50.
Alcaraz later said that nerves and tension during the match had caused his whole body to cramp up.
“At the beginning of the third set I started to cramp every part of my body, not only the legs. The arms, as well, every part of the legs,” he told reporters.
“It was really tough for me to move at the third set, and in the fourth set let’s say I had a little chance, but it was really tough … It’s not easy to play against Novak, of course he’s a legend of our sport. If someone says that he goes onto the court with no nerves playing against Novak, he lies.”
Win on Sunday and Djokovic will return to No. 1 in the world rankings and move ahead of Rafael Nadal at the top of the men’s all-time grand slam list.
“I like the feeling. It’s a privilege. It’s an incredible privilege to be able to make history in the sport that I truly love, and it has given me so much,” Djokovic told reporters.
“The motivation is very high, as you can imagine. There is one more to go, and hopefully I get my hands on the trophy.”