Never have these two teams been quite so dominant. Barcelona's 39-match unbeaten run in 2015-16 was the finest in the history of the Catalan club, but less than a year on, Real Madrid have matched it.
After going down 2-1 at Sevilla in October 2015, Barca did not lose again until defeat to Madrid in the Clasico last April. And even though Real lost their next match, a 2-0 defeat away to Wolfsburg, they have not been beaten since.
Barca's run came in one season, while Madrid's streak has arrived across two campaigns. So which of the two teams has the edge?