The 35-year-old was our top scorer last term with 28 in 46 appearances in all competitions last campaign, but he was released by the club having suffered a season-ending knee injury in April.
If fate hadn't intervened, Ibrahimovic would surely have hit the rare United landmark of 30 goals in a season and been able to savour the Europa League win in his home city on the pitch rather than in the stands.
United had allowed Ibrahimovic - who will take Wayne Rooney's number 10 shirt - to use the medical facilities at Carrington in his rehabilitation after surgery.
Up until the point that he ruptured his ligaments in that Europa League win over Anderlecht, it seemed almost certain that Ibra would stay with United for a second season.
Despite the fact he was not retained in June - and initial reports that he would be sidelined until 2018 - the club were always keen on the possibility of his return, provided the recovery went to plan.
It clearly has, with the Swede having shown almost superhuman powers of recovery to prove his fitness and earn a short-term deal until the end of the season.
Ibrahimovic is set to be fit again by December to finish what he started at Old Trafford, despite interest from Los-Angeles based MLS duo LA Galaxy and Los Angeles FC over the summer.
Even though he cannot yet play, United boss Jose Mourinho wants the Swede back to play a part in United's frantic festive fixture schedule and to bolster the attack during United's crucial run-in during the latter stages of the campaign.
The boss said: "Myself and everyone at the club are delighted that Zlatan is on the road to recovery and we are equally delighted to have his ambition and experience back with us.
"I have no doubt that he will be an important part of our squad for the second half of our season.
"After his contribution last season he deserves our trust, we have to be patient for his return but we have been impressed by his hard work and dedication to return to fitness."
There is a question mark over how Jose can accommodate the big man in the same team as Romelu Lukaku, but that answer will not be needed for a good while yet.
Welcome back Ibra