My partner passed away and didn't leave a will. How do I claim an inheritance?

What autonomous community are you or were you in? Because the process varies quite a bit depending on the region. In general, without a will, intestate succession comes into play, and you'll need to go to a notary or lawyer to start the proceedings. They'll ask you for the death certificate, identification documents, and proof of your relationship (marriage certificate or common-law partnership certificate). The notary will guide you on what assets you inherit according to the succession law that applies in your region, because the order of heirs changes if there are children, parents, or other relatives.

First thing is you should go to a notary as soon as possible, because without a will an intestate succession is opened and they'll guide you through all the paperwork. Keep in mind that the inheritance is divided according to the law of the community where you lived (which others have already mentioned), but here's a detail people forget: until you officially settle the estate, the two of you are still considered co-owners of the assets, and that makes it really complicated to withdraw money from joint accounts or sell properties. The notary will ask you for the death certificate, your marriage certificate, and documentation of the assets, so gather all that before you go.

Do you know if your partner had assets in another country or just in yours? The first thing is to go to a notary to start an ab intestato succession, but here's a detail a lot of people miss: before you do any official paperwork, gather all the documentation you can about the assets (debts, bank accounts, properties). That's going to speed up the whole process because the notary is going to need it anyway, and if you bring it already organized, you save time and money on back-and-forth trips. The notary will guide you according to your region's succession laws, but you definitely need to start there.