Inclusion Criteria:
* Participants are capable of giving signed informed consent which includes compliance with the requirements and restrictions listed in the Informed Consent Form.
* Male and/or female participants must be 18 years of age or older, at the time of signing the informed consent. In Republic of Korea, participants must be 19 years of age or older at the time of signing informed consent.
* Eastern Cooperative Oncology Group (ECOG) performance status 0-2.
* Participants with histologically or cytologically confirmed diagnosis of MM, as defined in International Myeloma Working Group criteria: 1. Has undergone autologous stem cell transplant (SCT) or is considered transplant-ineligible; 2. Has failed at least 2 prior lines of anti-myeloma treatments, including an immunomodulatory drug (example \[e.g.\], lenalidomide or pomalidomide) and a proteasome inhibitor (e.g., bortezomib, ixazomib or carfilzomib). In Republic of Korea, participants should also have relapsed or refractory disease after treatment with an anti-CD38 antibody, if accessible to patients, or other suitable local standard of care.
* Participants have measurable disease with at least one of the following: Serum M-protein \>=0.5 grams per deciliter (g/dL) (\>=5 grams per liter \[g/L\]); Urine M-protein \>=200 milligrams (mg) per 24 hours (mg/24 h); and Serum free light chain (FLC) assay: Involved FLC level \>=10 milligrams per deciliter (mg/dL) (\>=100 milligrams per liter \[mg/L\]) and an abnormal serum FLC ratio (\<0.26 or \>1.65).
* Participants with a history of autologous SCT are eligible for study participation provided the following eligibility criteria are met: 1. Transplant was \>100 days prior to study enrollment, 2. No active infection(s), and 3. Participant meets the remainder of the eligibility criteria outlined in this protocol.
* Participants with adequate organ system functions as defined follows: Absolute neutrophil count \>=1.0 x 10\^9 per liter (/L); Hemoglobin \>=7.0 g/dL or 4.9 millimoles per liter (mmol/L); Platelets \>= 50 x 10\^9/L; Total bilirubin \<=1.5 x Upper limit of normal (ULN) (Isolated bilirubin \>=1.5 x ULN is acceptable if bilirubin is fractionated and direct bilirubin \<35 percent \[%\]); Alanine aminotransferase \<=2.5 x ULN; iGFR, Group 1: normal/ mildly impaired \>=60milliliter per minute (mL/min); Group 2: severe 15-29 mL/min; Group 3: ESRD (not on dialysis) \<15 mL/min; Group 4: ESRD (on dialysis) \<15 mL/min; and left ventricular ejection fraction by echocardiograms \>=40%.
* Main additional inclusion criteria in Group 1 (matched control participants): Matched to at least one severely renal impaired participant by Baseline body weight (+/-20%) and Baseline albumin levels (+/-10%).
* Female participants: Contraceptive use by women should be consistent with local regulations regarding the methods of contraception for those participating in clinical studies. A female participant is eligible to participate if she is not pregnant or breastfeeding, and at least one of the following conditions applies: Is not a woman of childbearing potential (WOCBP) OR is a WOCBP and using a contraceptive method that is highly effective (with a failure rate of \<1% per year), preferably with low user dependency, during the intervention period and for at least 4 months after the last dose of study intervention and agrees not to donate eggs (ova, oocytes) for the purpose of reproduction during this period. The investigator should evaluate the effectiveness of the contraceptive method in relationship to the first dose of study intervention. A WOCBP must have a negative highly sensitive serum pregnancy test within 72 hours of dosing on Cycle 1 Day 1 and agree to use highly effective contraception during the study and for 4 months after the last dose of study medication. The investigator is responsible for review of medical history, menstrual history, and recent sexual activity to decrease the risk for inclusion of a woman with an early undetected pregnancy.
* Male participants: Contraceptive use by men should be consistent with local regulations regarding the methods of contraception for those participating in clinical studies. Male participants are eligible to participate if they agree to the following from the time of first dose of study until 6 months after the last dose of study treatment to allow for clearance of any altered sperm: Refrain from donating sperm and either; Be abstinent from heterosexual intercourse as their preferred and usual lifestyle (abstinent on a long term and persistent basis) and agree to remain abstinent; OR must agree to use a male condom even if they have undergone a successful vasectomy and female partner to use an additional highly effective contraceptive method with a failure rate of \<1% per year as when having sexual intercourse with a WOCBP (including pregnant females).
Exclusion Criteria:
* Participants with active plasma cell leukemia at the time of screening. Symptomatic amyloidosis, active POEMS syndrome (polyneuropathy, organomegaly, endocrinopathy, myeloma protein and skin changes), Waldenstroem Macroglobulinemia
* Participants had a prior allogeneic stem cell transplant. . Participants who have undergone a syngeneic bone marrow transplant will be allowed only if there is no history of, or no currently active graft-versus-host-diseases (GvHD).
* Participant has received an investigational drug within 14 days or 5 half-lives whichever is shorter, preceding the first dose of study drug. This includes prior treatment with a monoclonal antibody. The only exception is emergency use of a short course of systemic corticosteroids (equivalent to, or less than: dexamethasone 40 milligrams per day \[mg/day\] for a maximum of 4 days) before treatment.
* Prior belantamab mafodotin therapy.
* Participant has received a strong Organic-anion transporting polypeptide inhibitor within 14 days or 5 half-lives, whichever is shorter, preceding the first dose of study drug.
* Systemic active infection requiring treatment.
* Any unresolved toxicity \>=Grade 2 from previous treatment except for alopecia, or peripheral neuropathy up to Grade 2.
* Plasmapheresis within 7 days prior to the first dose of study drug. Screening laboratory values must be performed after last plasmapheresis.
* Any major surgery within the last 4 weeks prior to Day 1 of Screening.
* Any serious and/or unstable pre-existing medical, psychiatric disorder or other conditions (including lab abnormalities except renal impairment) that could interfere with participant's safety, obtaining informed consent or compliance to the study procedures.
* Evidence of active mucosal or internal bleeding.
* Current unstable liver or biliary disease per investigator assessment defined by the presence of ascites, encephalopathy, coagulopathy, hypoalbuminemia, esophageal or gastric varices, persistent jaundice, or cirrhosis. (Stable chronic liver disease \[(including Gilbert's syndrome or asymptomatic gallstones\]) or hepatobiliary involvement of malignancy is acceptable if participant otherwise meets entry criteria)
* Participants with previous or concurrent malignancies other than MM are excluded, unless the prior malignancy has been considered medically stable for at least 2 years. The participant must not be receiving active therapy, other than hormonal therapy for this disease. (Participants with curatively treated non-melanoma skin cancer are allowed without a 2-year restriction)
* Evidence of cardiovascular risk including any of the following: Evidence of current clinically significant untreated arrhythmias, including clinically significant electrocardiogram abnormalities such as second degree (Mobitz Type II) or third degree atrioventricular block; History of myocardial infarction (within prior 18 months), acute coronary syndromes (including unstable angina), coronary angioplasty, or stenting or bypass grafting within 3 months of Screening; Class III or IV heart failure as defined by the New York Heart Association functional classification system and uncontrolled hypertension.
* Known immediate or delayed hypersensitivity reaction or idiosyncratic reaction to drugs chemically related to belantamab mafodotin, or any of the components of the study treatment.
* Known human immunodeficiency virus infection, unless the participant can meet all of the following criteria: Established anti-retroviral therapy (ART) for at least 4 weeks and HIV viral load \<400 copies/mL prior to first dose; CD4+ T-cell (CD4+) counts ≥350 cells/ L and no history of AIDS-defining opportunistic infections within the last 12 months
* Participants with Hepatitis B will be excluded unless the following criteria can be met: If the participant is hepatitis B core antibody (HbcAb) positive or hepatitis B surface antigen (HbsAg) negative, then hepatitis B virus (HBV) deoxyribonucleic acid (DNA) should be undectectable at the time of screening; If HbsAg+ at screening or \<=3 months prior to first dose of study treatment, then HBV DNA should be undetectable, highly effective antiviral treatment should be started ≥4 weeks prior to first dose of study treatment. Participants with cirrhosis are excluded.
* Positive hepatitis C antibody test result or positive hepatitis C ribonucleic acid test result at Screening or within 3 months prior to first dose of study treatment unless the participant can meet the following criteria: RNA test negative and Successful anti-viral treatment (usually 8 weeks duration) is required, followed by a negative HCV RNA test after a washout period of at least 4 weeks prior to first dose.
* Participants with renal impairment due to hepatic disease (hepatorenal syndrome).
* Current corneal epithelial disease except for mild punctuate keratopathy.
* Participant is a woman who is pregnant or breastfeeding.
