This is an observational, multicentre epidemiological study with a longitudinal cohort in which information will be retrieved from medical records of patients with advanced metastatic or unresectable melanoma at first diagnosis.

Inclusion Criteria:

• Patients of legal age with stage III, metastatic, or unresectable melanoma at first diagnosis after January 8, 2018. First diagnosis is understood as: a. Disease onset as metastatic or unresectable disease; b. First metastatic or unresectable relapse in the pre-established dates (after January 8, 2018) in a patient with previous localised melanoma and completely resected on dates before the pre-inclusion period.
• Signing the Informed Consent Form (ICF).
• A patient may have received the first or subsequent treatments for metastatic or unresectable disease in a hospital other than the centre where the ICF was signed, as long as the patient meets the inclusion criteria 1.
• A patient can only sign one ICF (cannot sign an ICF in two different centres).
• If a patient signs the ICF in a centre during the first-line therapy and then goes to another centre with consideration for the following lines: If the centre is associated with the GEM-1801 study, researchers will do their best to update the following lines and the patient status, introducing the new information in the centre where the ICF was initially signed. This information will be provided by the patient before contacting the principal investigator and always with prior consent of the patient, who will have previously provided the consent to contact by telephone for this purpose. If this second (or subsequent) centre is not associated with the GEM- 1801 study, this will be considered loss of follow-up, unless the patient returns to the GEM-1801 start centre, wherein the reporting physicians will do their best to update the information from other centres, always with prior patient consent, who will have previously signed the ICF; c) A patient card with the assigned code will be delivered.

Exclusion Criteria:

• Any patient not complying with inclusion criteria.

A 'case' is defined as any patient, diagnosed, treated, or followed in the different health centres where reporting physicians authorised by the GEM group work, who meets the inclusion criteria.