The Karim Benzema-inspired Los Blancos lifted the Spanish league trophy after a 4-0 victory over Espanyol guaranteed them top spot with four games to go.
A double from Brazil winger Rodrygo, along with strikes from Marco Asensio and Benzema secured the silverware.
The result ends a title race which the Spanish giants have dominated from the start, despite some competition from Sevilla and a fightback from rivals Barcelona.
However, Xavi's inspiration in Catalonia wasn't enough to stop Ancelotti's side march to glory.
And the Italian has now completed one of the finest feats in managerial history.
The ex-Chelsea, Bayern Munich, Paris Saint-Germain and AC Milan head coach has now won a title in all of the top five European leagues.
It cements his legacy as one of the greatest coaches in football history.
Ancelotti is one of only three managers to win the Champions League/European Cup on three occasions, alongside Bob Paisley and Zinedine Zidane.
Meanwhile, in total he has won seven UEFA competitions, the joint-most along with Manchester United icon Sir Alex Ferguson and compatriot Giovanni Trapattoni.
And Ancelotti celebrated the triumph in style, picture puffing on a cigar during an open top bus parade in the Spanish capital.
Real Madrid's title glory was also significant for Brazil left-back Marcelo, who becomes the club's most decorated player.
The 33-year-old may now be reduced to a bit-part role with Los Blancos, but he's now got 24 medals in his collection over 16 seasons in the Spanish capital.
Real Madrid can still win one more trophy this term, but it will be a tough ask.
They lost 4-3 in the first leg of their Champions League semi-final with Manchester City, and will host the Premier League leaders in the return clash at the Santiago Bernabeu next.