An angry Leclerc dropped to fourth after Ferrari called him in again for slicks and then told him, too late, to stay out after Sainz also pitted and went directly from wets to the dry tyres.
Hamilton, who had also topped Saturday morning's final practice session, never look like being challenged throughout the qualifying hour.
Leclerc ended Ferrari's Italian Grand Prix win drought on Sunday
Red Bull's Max Verstappen, last year's winner at his team's home circuit, qualified third.
Red Bull's Dutch 20-year-old Max Verstappen took the chequered flag in second place with Kimi Raikkonen completing the podium for Ferrari and Australian Daniel Ricciardo finishing fourth for Red Bull.
The sky's the limit for George Russell after the British youngster's stellar performance
Max Verstappen won his home Dutch Grand Prix for Red Bull on Sunday and took the Formula One championship lead in front of a roaring, dancing army of fans hailing their hero with orange flags and flares.
Lewis Hamilton did 94 laps of Barcelona's Circuit de Catalunya on the soft C2 compound in a sunny afternoon session
Hamilton, who clinched his fourth world championship in Mexico two weeks ago, started from the pitlane after crashing in qualifying but led the race after 31 of 71 laps when others pitted.
It emerged then that former F1 racer Karun Chandhok's post-race video analysis for Sky Sports television formed part of what Ferrari had billed as "quite overwhelming" new and relevant evidence.
Ferrari's Sebastian Vettel won the Bahrain Grand Prix to go seven points clear at the top of the Formula One standings on Sunday, with Mercedes rival Lewis Hamilton staging a late charge to finish second.
Formula One world champion Max Verstappen won the inaugural Miami Grand Prix for Red Bull on Sunday, slashing Ferrari rival Charles Leclerc's overall lead from 27 to 19 points after five races.
World champion Max Verstappen took maximum points from Formula One's Imola sprint weekend, leading a Red Bull one-two on Sunday as Ferrari's homecoming turned sour for overall leader Charles Leclerc and his Italian team.
Hamilton has won the last three races, out of four so far in this COVID-19 affected season, and will start as favourite again.
Lewis Hamilton won his home British Grand Prix for a record-extending eighth time on Sunday despite a 10-second penalty for a controversial first lap collision that sent Red Bull rival Max Verstappen crashing out of the race.
Charles Leclerc crashed at the end of qualifying for his home Monaco Grand Prix on Saturday
Lewis Hamilton won the Monaco Grand Prix for Mercedes on Sunday, nursing his car's worn tyres to the finish in a nail-biting victory worthy of the team's late great Niki Lauda.
Austin is a favourite track for the 34-year-old Mercedes driver and he will also be fancied to round up his Texan win tally to six on Sunday.
Lewis Hamilton tested positive for COVID-19 and was forced to miss last year's penultimate Sakhir Grand Prix in December.
In an afternoon of heroes, Sebastian Vettel played the Bond villain at Silverstone, notes Raja Sen, who returns to Rediff.com as F1 columnist!
Reigning F1 champ warns Bottas about Hamilton rivalry
Images from the Russian F1 Grand Prix in Sochi on Sunday
Formula One world championship leader Sebastian Vettel won the Bahrain Grand Prix for Ferrari on Sunday in the German's 200th race start.
Qualifying took place at a sunny Suzuka on Sunday morning after being postponed from its usual Saturday slot due to the approach of Typhoon Hagibis.
Red Bull's Max Verstappen will be doing all he can to stop six-times world champion Lewis Hamilton completing a Mercedes hat-trick and matching another of Michael Schumacher's Formula One records in Hungary this weekend.
Verstappen led from start to finish at Austria's Red Bull Ring, with seven-time world champion Hamilton second for Mercedes.
The pole was a record-extending 88th of Hamilton's career and fifth of the season.
The German, whose bid for a fifth crown petered out last year in mistakes and misfortune, had already been facing questions about whether he was making too many errors to win the championship.
Formula One champion Lewis Hamilton won the Hungarian Grand Prix for a record seventh time on Sunday and extended his title lead to 62 points after relentlessly reeling in Red Bull's Max Verstappen.
Verstappen leads seven times world champion Hamilton by six points with six races remaining and the pole at Austin's Circuit of the Americas was the ninth of the season for the Dutch 24-year-old -- and eighth in the last 11 races.
Formula One world champion Lewis Hamilton won the Hungarian Grand Prix from pole position for Mercedes on Sunday to go into the August break with a 24-point lead over Ferrari rival Sebastian Vettel.
Verstappen took his 26th career win 0.9 of a second ahead of Spaniard Sainz,
The German, taking his fourth win of the season, took the chequered flag 0.9 seconds ahead of Kimi Raikkonen with Hamilton finishing fourth after sportingly surrendering third place to team mate Valtteri Bottas on the last lap.
Hamilton, eight points behind Vettel after 10 races, qualified 14th.
The Mercedes driver smashed the Monza track record with a sensational lap of one minute 18.887 seconds to lead team mate Valtteri Bottas in another front row lockout.
Ferrari's Charles Leclerc, starting on pole, finished second after defending hard against Verstappen with the two 21-year-olds banging wheels as the Dutchman forced his way past. Verstappen took the flag under investigation.
Alfa Romeo announced Guanyu Zhou as China's first Formula One racing driver on Tuesday with his arrival in 2022 hailed by both the team and the sport as a historic breakthrough in a key growth market.
IMAGES from the Silverstone F1 GP on Sunday
Max Verstappen put Red Bull on pole position for Formula One's season-opening Bahrain Grand Prix on Saturday, with seven times world champion Lewis Hamilton alongside on the front row for Mercedes.