Unlike France, where the forest leash season is seasonal and beach rules are purely municipal, Spain has a nationwide leash expectation written directly into Ley 7/2023, its animal welfare law. Article 27 prohibits companion animals from roaming public spaces without the direct, in-person supervision of their responsible person, which in practice means dogs must be leashed in public unless they're in a specifically designated off-lead area.
Cities apply this differently in the details: Barcelona has enforced it strictly since December 2023, with leashing required outside designated zones and some areas allowing off-lead use only during set morning and evening windows; Madrid allows off-lead use only from 7pm to 10am in winter and 8pm to 10am in summer, with some gardens banning dogs entirely; Valencia requires a leash except in designated areas and at times the city council sets. National parks, livestock grazing areas and other protected natural spaces are specifically called out as places where loose dogs are banned outright, not just discouraged.
Fines scale with the outcome, not just the act: reporting on the law describes a lower band of roughly €500 to €10,000 for letting a dog off-lead outside an authorised area with no other consequence, rising to €10,001–€200,000 if it leads to an attack on a person, a traffic accident, serious injury to another animal, or damage to a protected natural area — and notes that a standard pet insurance policy may not cover costs arising from a breach of this kind.