Midfielder Aleix Vidal fired inside the near post to put Almeria ahead in the 17th minute at their Juegos Mediterraneos stadium on the south coast.
Prolific striker Charles struck a second for the Andalusians seven minutes after halftime and put the tie beyond Girona when he made it 3-0 in the 70th minute.
"Finally," Almeria captain Corona said in a chaotic interview with Spanish television broadcaster Canal Plus, as team mates, technical staff and fans celebrated wildly on the pitch around him.
"All the people here deserve this and the team worked like trojans," he added.
"These are things you dream about when you are a kid," a champagne-soaked Vidal, stripped down to his underwear by jubilant fans, added.
Almeria return to the Spanish top flight after two seasons in the second tier while Catalonia-based Girona have never featured in La Liga.
Alicante side Elche, the second division champions, and second-placed Villarreal secured the two automatic promotion places. Real Zaragoza, Deportivo La Coruna and Real Mallorca were relegated from La Liga.