Dani Ceballos said he will give his all to make Real Madrid's history even greater after joining the Spanish and European champions.
The capital club paid a reported €18 million for the capture of the midfielder named Player of the Tournament in the European Under-21 Championship with Spain this summer.
"You cannot imagine the pride and responsibility I feel at having joined Real Madrid," he wrote via social media.
"I will give my all to make this club's history even greater.
"I come with great motivation and with the two things that have brought me here: humility and hard work.
"I will aim to show that I deserve to wear this shirt."
Ceballos played 30 games for Betis in La Liga last season, finishing with a record of two goals and two assists.