Puigdemont defiantly appeared in Barcelona on Thursday after travelling from Belgium and faces charges of embezzlement for his part in the attempt to break Catalonia away from the rest of Spain.
Puigdemont has dedicated his career to the goal of carving out a new country in northeast Spain - a struggle that is decades old.
His largely uncompromising approach has brought political conflict with other separatist parties as well as with Spain's central government.
Puigdemont appeared in a central Barcelona park where several thousand separatist supporters who had gathered in expectation of his arrival waved Catalan flags.
Supporters of Catalan independence leader Carles Puigdemont wait for his arrival in Barcelona. (AP PHOTO)
He punched the air to cheers on a bright, sunny day.
The event was organised by his political party Together for Catalonia (Junts) hours before a new regional government was to take office nearby.
Police were deployed in a security ring around a section of the park where Catalonia's parliament building is located behind walls.
Puigdemont walked towards the building followed by masses of supporters.
Puigdemont had earlier announced publicly he was going back to Spain, though he gave no travel details.
Puigdemont's presence in Spain is likely to generate renewed political tension over the smoldering issue of Catalan independence.
The failed secession attempt triggered a protracted constitutional crisis.
It was not immediately clear how authorities would proceed if Puigdemont was arrested.
A contentious amnesty bill, crafted by Spain's Socialist-led coalition government, could potentially clear Puigdemont and hundreds of other supporters of Catalan independence of any wrongdoing in the illegal 2017 ballot.
But the bill, approved by Spain's parliament earlier this year, is being challenged by the Supreme Court, leaving uncertainty about what crimes would be pardoned.
Puigdemont could initially be placed in pre-trial detention if he is arrested.
The former Catalan leader's return threatened to complicate a deal brokered after months of deadlock between Salvador Illa's Catalan Socialist Party and the other main Catalan separatist party and left-wing Esquerra Republicana.
That deal had ensured just enough support in Catalonia's parliament for Illa to become the next regional president in an investiture debate on Thursday.
