It was the first ever win for the visitor at the Bernabeu, and one that loosens Zinedine Zidane's grip on the managerial reins in Madrid. It was also the first time Los Blancos lost two consecutive league matches at home since February 2007.
Pablo Fornals neatly lobbed Keylor Navas for the winning goal after 87 minutes. The Costa Rican goalkeeper was stranded after blocking Enes Unal's effort, but it wasn't as straight-forward chance for Fornals who seemed to slow time down before lifting the ball above the crowd and into the onion bag.
With La Liga ambitions practically quashed, the clear priority at Real Madrid is attempting to capture a third straight Champions League crown. The club hasn't been handed a kind draw to begin the knockout stages - Paris Saint-Germain is its opponent in the round of 16 - and, if derisory results continue, Zidane may not be the man in the dugout for that challenge.
It's been a frustrating season for Real Madrid fans. A two-legged Supercopa evisceration of Barcelona in August fed hopes of another trophy-laden season under the Frenchman, but performances since have been well below par. The progression of youngsters into the first-team fold has stalled, and the big names in Zidane's squad aren't producing the goods either - Cristiano Ronaldo, Isco, Gareth Bale, and Marco Asensio top the club's scoring charts in the league with just four goals apiece.
If Barcelona wins at Real Sociedad tomorrow, Real Madrid will be closer to the relegation zone than first place.