Leclerc takes Monaco pole with crash-damaged Ferrari
Red Bull's Max Verstappen will set off alongside him on the front row of Formula One's iconic street race with world champion Lewis Hamilton in unfamiliar territory back on the fourth row.
Qualifying was red flagged at the end, depriving Hamilton and Verstappen of a late chance to better Leclerc's time with a flying lap.
With overtaking difficult on Monaco's tight and twisting circuit, Hamilton's chances of moving up to 99 grand prix wins look compromised.
After winning three out of four races this season the seven-time world champion leads Verstappen by 14 points in the drivers world championship.
"It's a shame to finish in the wall, it's doesn't feel the same but I'm incredibly happy about my lap," he said.
His mechanics face a long night carrying out repairs in the allotted time if Leclerc is not to pick up a penalty and lose his position at the head of the grid.
Hamilton's Mercedes teammate Valtteri Bottas set the third fastest time to take a place on the second row with Carlos Sainz in the other Ferrari for company.