Carlo Ancelotti's men need just five points from their last five games to ensure the title will return to the Santiago Bernabeu Stadium.
On a rainy Friday night in San Sebastian, Madrid put out a second-string team to rest Jude Bellingham, Vinicius Junior and other regulars for the visit to the Basque country.
The new faces struggled for large parts of the game with Sociedad enjoying much of the play and plenty of scoring chances.
But one of Madrid's new faces proved the difference between the sides.
Arda Güler, the 19-year-old Turkish attacker, made his first start in the league, and when the Sociedad defence failed to clear Dani Carvajal's low cross, Güler drifted in at the back post to slot the ball home with 29 minutes completed.
Takakura Kubo equalised three minutes later for Sociedad only to see his goal disallowed after a video review.
Ancelotti introduced Vinicius, Antonio Rudiger and Eduardo Camavinga in a busy second half as they fought to retain their lead and they held on to extend their unbeaten run in La Liga to 27 games.
Another satisfying note for the champions-elect was the return of Eder Militão. The Brazilian defender made his first start since tearing his cruciate ligament eight months ago, and played the entire 90 minutes.
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