Mr Rajoy said the unprecedented imposition of direct rule on Catalonia was essential to "recover normality".
He is also firing Catalan leader Carles Puigdemont and his cabinet.
The crisis began when Catalan leaders held an independence referendum, defying a ruling by the Constitutional Court which had declared it illegal.
The Catalan government said that of the 43% of potential voters who took part, 90% were in favour of independence. Others boycotted the vote after the court ruling.
- BBC -