The 20 year-old is leaving Logroñés to join La Fábrica.
The attacking midfielder will initially join Real Madrid C, who are seeking to recover their form after a difficult first half of the season.
Real Madrid are in 14th place in Group 5 of the Segunda RFEF, and Rezola's arrival is expected to bring quality and personality to their attack.
Rezola is a classic number ten: quick, creative, adept at finishing, and with a knack for scoring, as demonstrated by his two goals so far this season.
Having developed as a junior at Antiguoko, the same club that launched Xabi Alonso, before joining Real Sociedad, the young Basque arrived following an agreement between the clubs that allowed Madrid to beat out competition from Athletic Club and several foreign teams, including from Saudi Arabia.