Spain classifies certain dogs as potentially dangerous (perros potencialmente peligrosos, PPP) under Ley 50/1999 and Real Decreto 287/2002, and the official BOE text lists eight breeds in its Annex I: Pit Bull Terrier, Staffordshire Bull Terrier, American Staffordshire Terrier, Rottweiler, Dogo Argentino, Fila Brasileiro, Tosa Inu and Akita Inu, along with any cross of these. A dog that isn't one of these breeds can still be declared PPP if an authority assesses it as matching most of the physical traits set out in Annex II, or if it has shown markedly aggressive behaviour or bitten a person or animal.
Unlike France's category 1 dogs, no breed is barred from being brought into Spain at all — the system is a registration and licensing requirement, not an import ban. To hold a dog legally once you're in Spain, the owner needs a municipal licence (licencia), issued by the local town hall and valid for five years, which under the official decree requires being an adult with no relevant criminal record or serious prior sanctions, plus certificates of physical capacity and psychological aptitude, and civil liability insurance covering at least €120,000 — some autonomous communities (regions) set a higher minimum.
In public spaces and on public transport, a PPP dog must wear a muzzle suited to its breed and be controlled on a non-extendable leash or cord no longer than two metres, and one person may not walk more than one PPP dog at a time. The handler must carry the licence and proof of municipal registration when out with the dog. If you're bringing one of the listed breeds, or a dog that could plausibly be assessed as PPP by build, it's worth contacting the town hall where you'll be staying before you travel rather than after.

