This is one question that perplexes me: Was Catalonia ever a sovereign state? I understand that Catalonia was developed out of the Frankish counties of the Marca Hispania, but it still seems disputed whether Catalonia ever had sovereignty.
Was Catalonia ever a sovereign nation? Not quite, but it has come close.
The Catalan Counties were de facto ruled by Barcelona and declared independence from France. They eventually merged into the Count of Aragon. Although Catalonia was sovereign, the concept of nationalism didn't really exist before the 1700s.
The Catalan Republic declared independence in 1931 but immediately caved in to the central government.
Revolutionary Catalonia existed from 1936 to 1939. However, revolutionary Catalonia pretended to not be a state, and only controlled part of Catalonia.