The Spireites came from behind to beat Fleetwood Town 2-1 to clinch the Sky Bet League 2 title on a memorable, sun-soaked afternoon at the Proact.
Chesterfield were rocked when Matty Blair gave the visitors a 12th minute lead but goals from Sam Hird and Gary Roberts during a four-minute spell early after the re-start sealed the all-important win.
Fleetwood's Steven Schumacher fired over early on while Chesterfield's first chance fell to Eoin Doyle, who put a low shot wide.
Blair gave Fleetwood the lead, producing some trickery in the area and playing a one-two with Josh Morris before shooting low past Tommy Lee.
As the Spireites looked to make a quick response, Jay O'Shea's ball found Doyle in the area but he was forced wide and put his effort wide.
Morris then put a long-range effort off-target at the other end.
The Spireites then enjoyed a decent spell with Jimmy Ryan heading off-target from Nathan Smith's cross and Roberts putting a long-range effort off-target.
O'Shea also put a curling effort over after Ryan's free-kick had been blocked by the defensive wall.
Fleetwood threaded towards the end of the half with Gareth Evans seeing his shot deflected wide and Ryan Cresswell heading wide from a Morris corner.
Chesterfield were on the attack from the off at the re-start and they were level in the 50th minute when Hird headed past Chris Maxwell from O'Shea's cross.
After Ryan tested Maxwell with a firm, long-range drive which the keeper palmed wide, the Spireites took the lead.
The winner came in the 54th minute when Roberts received the ball on the right-hand side of the area and curled a superb effort beyond Maxwell.
The visitors threatened when Jon Parkin slipped a good ball through to Blair, but Smith made a great challenge inside the area to snuff out the threat.
Chesterfield applied pressure in search of a third goal with Smith having an angled shot saved and O'Shea's free-kick going narrowly off-target.
Roberts also went close with a curling effort and Dan Gardner, on as a replacement for Drew Talbot, saw his shot headed away by Cresswell.
O'Shea put an attempted chip straight at Maxwell and Gardner, on the right-hand side of the area, struck the side-netting with a shot.
The final whistle was blown after three minutes of stoppage time, sparking scenes of joy among fans, some of whom ran on to the pitch to celebrate with the players and management.
The trophy presentation was made on the pitch and the players were handed the medals before they went on a lap of honour, saluting all areas of the stadium.
The Spireites can now look forward to life in Sky Bet League 1.
Chesterfield: Lee; Talbot (Gardner 57'), Evatt (c), Hird, Smith; Ryan, Humphreys, Darikwa, O'Shea, Roberts (Togwell 84'); Doyle (Richards 80').
Subs not used: Dunbavin, Devitt, Beesley, Gnanduillet.
Fleetwood Town: Maxwell, Murdoch, Evans, Schumacher (c), Parkin, Hogan, Cresswell, Blair, Taylor, Morris (Hughes 72'), Jordan.
Subs not used: Davies, Roberts, Sarcevic, Allen, Ball, Barton.
Chesterfield - Hird 50', Roberts 54'
Fleetwood Town - Blair 12'
Attendance: 9,037 (261 Fleetwood Town)