ParanÃ is bounded on the north by SÃ # o Paulo , on the east by the Atlantic Ocean , on the south by Santa Catarina and the Misiones Province of Argentina , and on the west by Mato Grosso do Sul and the republic of Paraguay , with the ParanÃ River as its western boundary line . ParanÃ is bounded on the north by SÃ # o Paulo state , on the east by the Atlantic Ocean , on the south by Santa Catarina state and the Misiones Province of Argentina , and on the west by Mato Grosso do Sul and the republic of Paraguay , with the ParanÃ River as its western boundary line .