The withdrawal of two-time champion Murray means Djokovic is the only member of the fabled "Big Four" in the men's draw at the All England Club.
Roger Federer has retired and Rafael Nadal opted to skip Wimbledon to prepare for a shot at another Olympic title.
Murray, 37, is hoping to end his stellar career at the upcoming Paris Games but desperately wanted to make a final singles appearance at Wimbledon, where he was champion in 2013 and 2016.
The Scot, who has been ravaged by injuries in recent years, will still play doubles with his brother Jamie in what is bound to be an emotional farewell in front of his adoring British fans.
Murray underwent surgery to remove a cyst from his back last month after being forced to pull out of Queen's, a procedure he described as "not insignificant".
But he admitted defeat in his race to be fit on Tuesday.
"Unfortunately, despite working incredibly hard on his recovery since his operation just over a week ago, Andy has taken the very difficult decision not to play the singles this year," said a statement from Murray's representatives.
"As you can imagine, he is extremely disappointed but has confirmed that he will be playing in the doubles with Jamie and looks forward to competing at Wimbledon for the last time."
Murray was replaced in the draw by Belgium's David Goffin, a lucky loser from qualifying.
History-chasing Djokovic
Djokovic, born a week apart from Murray in May 1987, had a knee operation after pulling out before his French Open quarter-final -- sparking fears he would not be fit in time for Wimbledon.
But the Serbian world number two, who was beaten by Carlos Alcaraz in last year's final, has said he is "pain-free" and opens against Czech qualifier Vit Kopriva.
He knows time is not on his side as he bids to equal Federer's Wimbledon title record and become the first player -- man or woman -- to win 25 Grand Slam singles titles.
"I do have something that is described as a feeling of not missing out at a Grand Slam while I can still play and while I'm still active and at this level," said the Djokovic, who has reached the past five finals at the All England Club.
"I wouldn't call it a fear of missing out. I would just say it's this incredible desire to play, just to compete.
"Particularly because it is Wimbledon, the tournament that always has been a dream tournament for me when I was a kid. Just the thought of me missing Wimbledon was just not correct. I didn't want to deal with that."
Also in action on the second day of the Championships is women's world number one and five-time Grand Slam champion Iga Swiatek, eager to progress beyond the quarter-finals for the first time.
Swiatek, 23, arrives at the All England Club on the back of a 19-match winning streak but with lingering questions over whether she can transfer her clay-court form to the grass.
First up for the Polish player is Sofia Kenin, whom Swiatek defeated in the first round of the Australian Open this year.
Marketa Vondrousova launches her title defence against Spain's Jessica Bouzas Maneiro while 2022 champion Elena Rybakina is also in first-round action.
Ons Jabeur, the beaten finalist in 2022 and 2023, takes on Japan's Moyuka Uchijima.
