While Ralf claimed the second pole position of his career, older brother Michael's run of poles for Ferrari came to an end after a highly strategic session on Saturday when cars qualified on different fuel levels under new regulations.
World champion Michael qualified fifth fastest after starting the last three races on pole. The Ferrari driver has also won the last three and is seeking a record-equalling sixth Monaco success this weekend.
Williams have not won in Monaco since 1983.
Ralf lapped in one minute 15.259 seconds, 0.036 faster than Raikkonen, who leads Ferrari's Schumacher by two points after six races.
Colombian Juan Pablo Montoya put his Williams on the second row alongside Renault's Italian Jarno Trulli.
Michael Schumacher will line up alongside the McLaren of Briton David Coulthard, winner last year and in 2000, with Brazilian Rubens Barrichello behind him in the second Ferrari and Spaniard Fernando Alonso eighth for Renault.
Briton Jenson Button, third in Thursday's first qualifying, was absent after crashing his BAR heavily in the morning free practice.
The 23-year-old must wait to hear on Sunday whether he has been cleared to start the race.
