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Needing a point to lift the title, Ards were 2-0 up at half-time thanks to a Ross Arthurs strike and an own goal by visiting keeper Gareth Buchanan.
Niall Currie's men added a third after the break through Carl McComb.
H&W Welders beat Bangor 1-0 to finish runners-up, three points behind Ards, and Institute go into the play-off.
With the Welders, Armagh and Knockbreda not having Premiership licences, fifth-placed Institute go into the promotion/relegation game over two legs against Ballinamallard United who finished one-from-bottom of the Premiership.
Institute lost 1-0 to Ballyclare but just edged their place on goal difference from Larne who hammered Lisburn Distillery 6-1.
Ards, who play at Bangor's home ground, last played in the top flight in 2014 when they were relegated.
On Thursday night they missed their first chance to clinch the title by losing 2-0 away to Knockbreda.
But they made no mistake on Saturday against mid-table Loughgall.
Arthurs put them into a 37th-minute, pouncing after McComb's initial effort had been well saved by Buchanan.
The second goal quickly followed as Craig McMillen's inswinging corner was punched into the net by keeper Buchanan.
McComb cut inside to complete the scoring with a composed finish in the 58th minute.
As Ards celebrated their triumph, they held up the number eight shirt of team-mate Gary Warwick who had been seriously injured in an assault in Belfast six days earlier.
The midfielder suffered a fractured skull and bruising to the brain in the city centre attack.
After the match on Saturday, the Ards players wore tee-shirts bearing Warwick's photograph and the message 'this one's for you Gary'.
Ards clinched the Championship One title and promotion to the Irish Premiership by beating Loughgall 3-0 in their final game of the season.