Welshman Bale, the world’s most expensive player, gave Carlo Ancelotti’s side the lead with an early header at the Bernabeu and he soon turned provider for Karim Benzema to net the second.
His cross from deep on the right flank found the Frenchman and the ex-Lyon man headed past goalkeeper Diego Marino, meaning that he has now scored in five successive La Liga matches.
The second half saw Bale add to his tally after Marcelo's low cross was only half cleared by the Valladolid defence and the former Tottenham man then completed his treble in the 89th minute, as the injured Cristiano Ronaldo watched on from the stands.
Madrid's city rivals Atletico remain three points ahead them in the table, however, after their fine win.
Koke opened the scoring after 63 minutes for Diego Simeone men when he pounced on poor goalkeeping by Manu Herrera.
Diego Costa's brilliant season continued as he notched his 15th league goal of the campaign. Adrian's cross looked set to be caught by Manu, but the Brazilian beat him to it and scored from point-blank range.
Celta Vigo managed to open up a gap between themselves and the bottom three thanks to a 3-1 win over Almeria, who stay in 18th place.
On-loan Liverpool midfielder Suso gave the visitors a ninth-minute lead with an excellent finish from outside the area, but it was short-lived.
Chilean Fabian Orellana equalised in the 26th minute with a similarly impressive strike after cutting in from the left, before Borja Oubina put Celta ahead just after half-time with a close-range finish.
Charles – a close-season signing from Almeria – made sure Celta claimed all three points just before the hour mark with a flicked effort at the front post.
Saturday's late kick-off saw Espanyol host Real Sociedad at Cornella-El Prat, with the visiting side claiming all three points courtesy of a late own goal in a 2-1 win.
Forward Jhon Cordoba struck for the hosts in the 31st minute to break the deadlock - the 20-year-old Colombian finishing after a clever run down.
Jagoba Arrasate's men were kept out for most of the match, but Antoine Griezmann eventually drew them level 22 minutes from time as he headed in Carlos Vela's cross from deep before Christian Stuani diverted the ball past his own goalkeeper in the closing stages.
