Sevilla's defeat at the Bernabeu as they will finish fourth and Atletico Madrid, who drew 1-1 at Real Betis, will qualify automatically for next season's Champions League in third.
Real's Champions League triumphs in 2014 and past year have distracted from rivals Barcelona's creeping domination in the domestic league, with the Catalan side winning five of the last seven titles. Madrid's final game is at Malaga.
And while Barca seem to have to play well to win matches and especially titles, Madrid showed again on Saturday that their speciality is grinding out results with ruthless performances.
EmpicsWilliam Ralph "Dixie" Dean spent 13 years terrorising defences with Everton and his tally would have been 37 goals higher had the Toffees not spent the 1930-31 season in the second division. "Celta are a professional team and will go out to win, nothing less". Granada and Osasuna had already been demoted.
However, the visitors went straight up the other end and Marcelo's low cross was tapped home by Karim Benzema to restore Real's two-goal cushion.
Picking up the ball in what seemed like a safe area Ronaldo looked up and fired an unstoppable left-footed drive into the back of Sergio Alvarez's net.
Nacho made sure that the edgy atmosphere inside the Bernabeu never arrived with this bit of quick thinking.
Ronaldo has also played at Portuguese side Sporting Lisbon, who sold him to Manchester United for €19 million in the summer of 2003.
After Nacho Fernandez had given Madrid a controversial 10th-minute lead with a quickly-taken free-kick, Ronaldo reached the milestone with a simple tap-in to make it 2-0 in the 23rd minute.
And Kroos rounded off the scoring himself by prodding into the far corner 6 minutes from time.
But it was Nacho's opening goal for Real that should frustrate Barcelona fans the most.
Meanwhile, if they draw, they would need to win on the final day, or failing that, match whatever Barcelona do.
"Our daily job is to win the league". Las Palmas temporarily gained a foothold in the game, as Pedro Bigas scored just after the hour mark.
We'll all be supporting Celta tonight as they welcome Real Madrid to Balaidos in a game that will have huge ramifications for the destination of the title. "It wasn't an easy match".