Systemic sclerosis (SSc) is a chronic autoimmune multiorgan disease with high mortality. Localized scleroderma, or morphea, is a rare autoimmune disorder characterised by inflammation and fibrosis of the skin. The aim of this study was to examine the incidence of SSc and its changes in Finland after introducing the new classification criteria in 2013, the causes and predictors of death among Finnish SSc patients, as well as the clinical features, comorbidities and treatments of morphea patients in Southwest Finland. The study population comprised SSc patients treated in the hospital districts of Southwest Finland and Northern Ostrobothia during the years 1996–2018, death certificates of deceased patients from both hospital districts during the years 2000–2020. For the study of morphea, the study population comprised patients with morphea in Southwest Finland between 2005 and 2020. During a 20-year follow-up period divided into 5-year intervals, the incidence of SSc in Finland increased significantly utilising the most recent criteria, but not with the older ones. The increase was observed in the limited cutaneous systemic sclerosis (lcSSc) subgroup, suggesting that the more sensitive criteria identify milder disease forms. A considerable proportion of patients with SSc died as a direct consequence of the disease, in both the lcSSc and diffuse cutaneous systemic sclerosis (dcSSc) subtypes (33% and 52%, respectively). Cardiopulmonary complications were the most common SSc-related causes of death. Patients who died due to SSc were younger, and mortality occurred earlier in the disease course compared to patients who died from other causes. The identified prognostic factors were consistent with the previous findings in the literature. In Southwest Finland, morphea showed two age-related incidence peaks, occurred more frequently in females, and its incidence did not increase. The coexistence of other autoimmune diseases, particularly thyroid and skin diseases, was common, while concurrent SSc was rare (1.9%). The risk of malignancy was not increased. Extracutaneous manifestations were more common among pediatric onset patients than adult-onset patients. Methotrexate was the most commonly used systemic treatment, and both methotrexate and phototherapy benefitted the majority of treated patients. These retrospective studies provide valuable insights into two relatively rare autoimmune diseases and their frequencies, prognostic factors, and comorbidities. The results may support clinical decision-making. The identification of prognostic factors can guide patient follow-up and facilitate more targeted screening for organ involvement and comorbid conditions.