The Brazilian striker, who had hit a minor drought after failing to score for three games, produced two brilliant finishes either side of the break and then served up a third for Luis Figo as he turned in a match-winning performance at the Bernabeu.
Earlier Deportivo, who lost 2-0 at home to Real Mallorca in midweek, turned in a lame performance in their goalless draw against a determined Murcia at the Condomina stadium.
Real now lead the table with 23 points from 10 games, one ahead of Depor and three clear of Valencia, who make the trip to play Real Mallorca on Sunday.
Despite the apparently comfortable scoreline, Bilbao pushed Real hard throughout the 90 minutes and it took a string of stunning reflex saves from keeper Iker Casillas to keep the champions in the game early on and deny the visitors a deserved goal.
David Beckham, returning to the starting line-up after two games out with a pulled hamstring, showed little sign of his injury as he too produced a fine performance at the heart of the Real midfield.
The England captain sprayed a series of pin-point passes around the pitch and came close to scoring with a well-struck dipping free kick in the second half.
But the former Manchester United player was fortunate to stay on the pitch when he escaped with just a booking -- his third in 10 games -- when he brought down Andoni Iraola as the Bilbao defender raced towards the Real area in the final minute of the half.
SPRIGHTLY START
Bilbao made a sprightly start at the Bernabeu and created two clear scoring chances in the opening 10 minutes, but sharp saves from Casillas denied the Basques an early lead.
The Real keeper made a great point-blank save to block a bullet header from Santi Ezquerro on five minutes and then got down quickly to turn away a Jonan Garcia shot after a lightning break initiated by pacy winger Joseba Etxeberria.
The two sides proceeded to trade attacks in a pulsating first half, Casillas coming to Real's rescue twice more when he saved an Etxeberria effort with his foot and then tipped a goal-bound Tiko free kick over the bar.
But it was the deadly finishing of Ronaldo that finally broke the deadlock. Lurking inside the area, the Brazilian controlled a loose ball with his shoulder, turned sharply and sent a cracking right-foot shot fizzing inside the far post on 34 minutes.
Bilbao continued to press after the break, but once again it was Ronaldo's contribution that proved decisive.
He fended off three Bilbao players with a dazzling jinking run before finishing off with a perfectly placed shot from the edge of the area -- this time with his left foot -- to make it 2-0 on 55 minutes.
The Brazilian, who now tops the scoring charts with eight goals, completed a vintage performance when he unselfishly set up Real's third for Figo.
Skipping past one defender, he then left another on his back as he checked towards goal before laying the ball off to the Portuguese international who slotted home into the untended net.
