Souza's stoppage-time header earned Fenerbahce a dramatic 1-0 win at rivals Galatasaray in the Super Lig on Sunday.
The Istanbul derby is one of the most hotly-contested matches in world football, but with Fener and Gala third and fourth in the table at kick-off there was little hope of either catching leaders Besiktas and winning the league.
Gala dominated the first half but Yasin Oztekin and Wesley Sneijder saw shots saved by Fener goalkeeper Volkan Demirel, while Robin van Persie went closest for the visitors.
Clear-cut chances remained hard to create for both sides after the interval and the match appeared to be drifting towards a goalless draw.
But Souza had other ideas, rising highest in the box to power a tremendous header past Fernando Muslera from a right-wing Sener Ozbayrakli cross to snatch all three points for his side.
Fener consequently cut the gap to league leaders Besiktas – who play their game in hand against Adanaspor on Monday – to eight points, but bragging rights were the main prize after Dick Advocaat's men completed the double over their old rivals.