Sam Curtis banged in the winner in the 16th minute with Spireites hanging on to that lead for three valuable points.
It leaves them sixth in the league and with a two points cushion inside the play-off places.
Here are just some of the fans who saw the game, taken by Tina Jenner.
Get more Spireites news here.
9. Spireites 1 Gillingham 0
Chesterfield moved into the play-offs with a battling win over Gillingham. Photo: Tina Jenner
10. Spireites 1 Gillingham 0
Chesterfield moved into the play-offs with a battling win over Gillingham. Photo: Tina Jenner
11. Spireites 1 Gillingham 0
Chesterfield moved into the play-offs with a battling win over Gillingham. Photo: Tina Jenner
12. Spireites 1 Gillingham 0
Chesterfield moved into the play-offs with a battling win over Gillingham. Photo: Tina Jenner
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