Nathan Broadhead came off the bench to head home a stoppage-time winner and send Alex Neil’s side back into the League One play-off places.
The striker had missed the team’s last three matches with a hamstring injury but made the difference against a compact Gills defence.
Sunderland now have six games remaining as they try to secure a play-off place.
Our chief SAFC writer Phil Smith has delivered his verdict on how each Black Cats player fared at the Stadium of Light:
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13. Nathan Broadhead (sub) - 7
Looked sharp as usual on his return from injury and held his nerve with a deft header to win it. Welcome back. 7 Photo: JPI Media
14. Lynden Gooch (sub) - 6
Brought some energy to the right flank and played a couple of good crosses that probably could have yielded a bit more. 6 Photo: Frank Reid
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