Stanningley, who finished second in the table two places ahead of Leigh, scored five tries to three, none of them converted in blustery conditions at Manchester Regional Arena.
Their second successive Grand Final win was compensation after Stanningley controversially missed out on top spot in the table.
They needed to beat Widnes by 53 points in their final game to become league leaders, but – according to Stanningley coach Darren Woods – the visitors refused to play on after trailing 50-0 at the break.
The result stood so Stanningley had to settle for runners-up spot, but they made amends with a spirited performance in the title decider.
The Leeds side led 8-4 at half-time through tries by Fielding and Jodie Davies.
Leigh, whose Charlotte Hill crossed in the opening 40, levelled within moments of the restart when Megan Eastwood touched down.
Fielding squeezed over at the corner for her second try and then Vikki Hayley crashed over to put two scores between the sides.
Fielding turned try saver to force Hill into a knock-on over the line, but Leigh cut the gap through Leanne Johnson.
The game was in the balance until Fielding grabbed her third try five minutes from time to complete the scoring.
Woods felt the Grand Final win was what Stanningley deserved at the end of a fine season.
“We were confident,” he said.
“We made hard work of it, but we got there in the end and got just reward.
“They threw ball about, but we were solid in defence and grit and determination towards the end got us over the line.
“We had that in abundance.”
Stanningley: Spencer, A Waller, Morgan, Fielding, L Waller, Wainwright-Morley, Dyson, V Hayley, Davies, Gregory, J Davies, E Hayley, Woods. Subs: Fisher, K Hayley, Cunnett, Barker, Bickerdyke, Brierley, Hay.
Leigh Miners Rangers: Morley, Johnson, Burke, Hill, Leigh, Marsh, Quinn, Dainty, Banks, Farrimond, Young, Gray, Eastwood. Subs: Ward, Porter, Morris, Organ, Hancock.
Referee: Neil Pascall.