Inclusion Criteria:

1. Body weight ≥ 40 kg at screening
2. Willingness and ability to comply with all study visits and procedures
3. Documented diagnosis of PNH, confirmed by high sensitivity flow cytometry
4. LDH Levels ≥ 2x the ULN at screening
5. Participants who have at least four transfusions during 12 months prior to screening (documented in the medical record)
6. Presence of one or more of the PNH-related signs or symptoms within 3 months of screening
7. Vaccination against Neisseria meningitidis serotypes A, C, W, and Y < 3 years prior to initiation of study treatment (Day 1)
8. Vaccination against Haemophilius influenzae type B and Streptococcus pneumonia according to national vaccination recommendations
9. For participants receiving other therapies (e.g., immunosuppressants, corticosteroids): stable dose for ≥ 28 days prior to screening and up to the first drug administration
10. Adequate hepatic and renal function
11. Women of childbearing potential: agreement to remain abstinent (refrain from heterosexual intercourse) or use contraception during the treatment period and for 46 weeks (approximately 10.5 months) after the final dose of crovalimab
12. Platelet count ≥30,000 per cubic millimeter (mm^3) at screening
13. ANC > 500/microlitres (μl) at screening

Exclusion Criteria:

1. Current or previous treatment with a complement inhibitor
2. History of allogeneic bone marrow transplantation
3. History of Neisseria meningitidis infection within 6 months prior to screening and up to first drug administration
4. Known or suspected immune or hereditary complement deficiency
5. Known HIV infection with cluster of differentiation 4 (CD4) count < 200 cells/µl within 24 weeks prior to screening
6. Infection requiring hospitalization or treatment with IV antibiotics within 28 days prior to screening and up to the first drug administration, or oral antibiotics within 14 days prior to screening and up to the first drug administration
7. Active systemic bacterial, viral, or fungal infection within 14 days before first drug administration
8. Presence of fever (≥ 38˚C) within 7 days before the first drug administration
9. Splenectomy < 6 months before screening
10. History of malignancy within 5 years prior to screening and up to the first drug administration
11. Pregnant or intending to become pregnant during the study or within 46 weeks (10.5 months) after the final dose of study treatment
12. Participation in another interventional treatment study with an investigational agent or use of any experimental therapy within 28 days of screening or within 5 half-lives of that investigational product, whichever is greater