The “la Caixa” Foundation offers 20 Postdoctoral Junior Leader fellowships to support outstanding researchers of any nationality in carrying out postdoctoral research projects in STEM disciplines at universities or research centres in Spain or Portugal. Supported fields include life sciences, experimental sciences, physics, chemistry, engineering, technology, and mathematics. Each fellowship has a maximum duration of three years, with funding of up to €320,100, and includes a structured training programme in multidisciplinary and transferable skills to support career development. Applicants must have obtained their PhD between two and seven years before the call’s closing date, calculated from the date of thesis defence. Candidates are also required to have completed at least six months of research experience abroad during their doctoral or postdoctoral training. Mobility rules apply: candidates must not have lived or carried out their main activity in Spain or Portugal for more than 12 months during the three years preceding the deadline, depending on the host country. Special provisions exist for candidates with interrupted research careers or refugee status. Only complete and eligible applications will be considered.