Goals by Gary Hooper and Georgios Samaras had the game tied up by the interval but an emphatic Light Blues victory at Kilmarnock made it academic.
Celtic substitutes Shaun Maloney and Paddy McCourt grabbed further goals to secure an easy victory but it was not enough to prevent the Hoops finishing second to Rangers for the third successive season.
Celtic's title task beforehand was clear yet difficult - the Parkhead side had to get a better result than the Light Blues could muster in Ayrshire to win the SPL.
However, any chance of a last-day title turnaround ended at Rugby Park when Rangers raced into an early three-goal lead which they built upon.
The Celtic game turned in to something of a tribute to Neil Lennon, who has had to endure a wretched first season as permanent Hoops boss.
The former Parkhead skipper found himself once more in the national spotlight after being the subject of an attempted attack by a fan during the 3-0 win against Hearts at Tynecastle on Wednesday night.
The following morning, Lennon, who had bullets and parcel bombs sent to him earlier in the season, was told that a package containing what appeared to be another bullet was delivered to him at Parkhead.
The Irishman will take some strength from the backing he has been given and he showed his appreciation after the game when he said: "This is not the end, this the beginning."
Lennon may point to the shock defeat at Inverness or Rangers keeper Allan McGregor's penalty save from Samaras at Ibrox as turning points in the title race but the fact remains that rivals Rangers clinched their third successive title.
He will get the chance to make amends, in part, when Celtic play the Fir Park side in the Scottish Cup final at Hampden next week.
With that in mind, Motherwell showed five changes with manager Stuart McCall refusing to take risks with players ahead of the showpiece occasion.
Inside a minute some hesitation in the Hoops' defence allowed Motherwell midfielder Steve Jones a chance to shoot but his drive went wide.
News of an early goal for Rangers dampened the enthusiasm inside the stadium and moments later Celtic defender Daniel Majstorovic headed Ki Sung-yueng's free-kick wide of the target.
Another two goals for the Light Blues in Ayrshire looked to have ended any Celtic hopes but they kept at their task and in the ninth minute Lee Hollis made a great block from Samaras, before Forrest blazed over the bar seconds later.
In the 10th minute Hollis made another fine save, this time parrying clear Hooper's right-footed drive.
In the 18th minute Lennon emerged from the dugout to take the orchestrated acclaim of the Celtic support, just as Motherwell defender Shaun Hutchinson headed over the Hoops' bar.
Moments later, Hollis did well to foil Hooper before Hoops skipper Scott Brown fired the loose ball inches wide.
Hutchinson nearly put Samaras' low cross from the right in to his own net, the defender happy to see his clearance from six yards go for yet another corner which came to nothing.
But on the half-hour mark Celtic's pressure paid off when Hooper finally put them ahead.
When right-back Mark Wilson's cross came in to the packed Well box, Hooper got the break of the ball before poking it past Hollis from eight yards.
Celtic turned the screw further and Hollis made another save in the 36th minute, this time from Ki's angled drive, before making another block from the same player moments later.
But in the 40th minute the Fir Park keeper was helpless again when Samaras had the easy task to slide the ball in from 12 yards after being set up by Charlie Mulgrew.
Hollis capped a terrific first-half performance when he tipped an attempted lob by Samaras over the bar to prevent a third goal.
With the points surely secured, Maloney replaced Celtic left-back Emilio Izaguirre at the break, with Mulgrew moving to left-back.
Within seconds of the restart Maloney was sent racing through the middle of the Motherwell defence by Hooper but he screwed his shot wide under pressure from Hollis.
However, in the 53rd minute Maloney drove past Hollis from 12 yards after creating space for himself to make it 3-0.
Celtic supporters, in some defiance at their fate, celebrated in the style of Manchester City fans with their backs to the pitch and were given a round of applause by the players.
The game had become almost irrelevant as Lennon again waved in appreciation of the fans' backing.
In the 66th minute, as the tempo dropped further, Jonathan Page came on for Hutchinson while McCourt replaced Forrest and five minutes later the former Derry City player drove past Hollis to make it four.
The game free-wheeled towards conclusion as the home fans went through a repertoire of chants in appreciation of former players.
Maloney sent a couple of efforts wide of the target before the final whistle brought the curtain down on an ultimately disappointing league campaign.