Hamilton had been looking to match Michael Schumacher's record of 91 wins in Formula One but had to settle for third behind Bottas and Max Verstappen.
Mercedes' Hamilton on Saturday took his 96th pole position ahead of the Russian Grand Prix and would be looking to equal Schumacher's record of 91 race wins on Sunday.
Hamilton charged to a track-record time of 1 minute, 31.304 seconds, beating the Red Bull of Max Verstappen by .563 for his fifth straight pole position.
Hamilton's time of 1 minute, 33.279 seconds was the fastest of the latest Formula One round so far and .776 better than his Mercedes teammate Valtteri Bottas, who had been quickest in the first two sessions.
But Hamilton's focus was elsewhere as he stood on the podium wearing a T-shirt featuring the words “Arrest the cops who killed Breonna Taylor." The blunt message was in capital letters on the front of his black shirt.
The first F1 race on a Mugello track with super-fast corners usually used by MotoGP riders was incident-packed throughout.
While Hamilton clinched a record-extending 95th pole, it was hard luck for Bottas. He now trails Hamilton 7-2 this season in poles all won by Mercedes.
Quickest in both sessions on Friday, he beat Red Bull’s Max Verstappen by just .017 with Formula One champion Lewis Hamilton .083 back from Bottas in third in warm and sunny conditions.
It was Gasly's first-ever win in Formula One. The 24-year-old Frenchman finished 0.415 seconds ahead of McLaren driver Carlos Sainz and 3.358 ahead of Racing Point's Lance Stroll on a surreal-looking podium.
Hamilton looks on course to extend his championship lead, which stands at 47 points from Red Bull rival Max Verstappen and 50 from Bottas.
The championship leader finished .262 ahead of Bottas, who was quickest in first practice. McLaren driver Lando Norris was third, .897 slower than Hamilton.
The Finnish driver’s best lap was .245 seconds quicker than Hamilton and .797 ahead of Red Bull driver Alexander Albon.
Hamilton's fifth win from seven races also extended his championship lead over Verstappen to 47 points with Bottas drifting back in third. Hamilton is odds-on to win a seventh title to tie Schumacher's record.
Hamilton is primed to extend his championship lead, which stands at 37 points over Red Bull's Max Verstappen and 43 over Bottas.
The Formula One champion was 0.23 seconds faster than Renault's Esteban Ocon and 0.39 quicker than McLaren's Lando Norris.
The Finnish driver's best lap was .069 seconds quicker than his Mercedes teammate Lewis Hamilton, who leads the championship after winning four of the first six races.
Hamilton, a six-time F1 champion and the only Black driver in the sport, said he supported the boycotts but that similar measures in Europe wouldn't have the same impact.
The talk before the race was whether Mercedes' tires would be vulnerable in the searing summer heat of Spain, after experiencing problems in the last two races at Silverstone.
Bottas was ahead of championship leader Hamilton on the first two splits but lost a fraction of time when he came out too wide from a turn at the end of his lap
Hamilton was 0.151 seconds clear of Mercedes teammate Valtteri Bottas and 0.515 in front of Red Bull's Max Verstappen. McLaren's Carlos Sainz Jr. showed impressive pace and ended fourth.
Top News
Latest News
