Djokovic won 5-7 2-6 6-3 6-2 6-2 in three hours and 35 minutes for his 26th consecutive Wimbledon match win, moving two steps away from a fourth successive title at the All England Club.
It gave him a 10th victory in the 11 five-set matches he has contested at Wimbledon, a fourth-round loss to Mario Ancic in 2006 the exception.
From 4-1 ahead in the second set, Djokovic's game went into sleep mode for an hour as his inspired Italian opponent stole a march, Sinner threatening to pull off a shock to follow up his outstanding fourth-round win over Carlos Alcaraz.
Sinner was profiting from Djokovic's lethargic and erratic display, the crowd lending him their full support, which was no doubt jarring for Djokovic given his status as one of the tournament's greatest champions.
Djokovic gained a foothold in the contest by breaking to love to lead 3-1 in the third set, beckoning to the crowd to show him a little love in the next game.
From that point he never looked back. The tide was not so much turning but lapping urgently at the Sinner shoreline, threatening to wash away his challenge, and when he conceded a break in the third game of the deciding set the script was almost complete.
Sinner had rolled an ankle at the end of the fourth set but was quickly back to his feet, only to be mowed down by the relentless Serbian juggernaut on the other side of the net, a highlights-reel crosscourt backhand winner from Djokovic crowning the comeback as the winning line approached.