Phase 2/3 Inclusion Criteria (applicable for both adult and pediatric subjects): 1. Males or females aged ≥5 years at the time of consent. 2. Subjects who have confirmed clinical and CLIA certified or equivalent genetic diagnosis of Stargardt disease (including ABCA4 related retinopathies). 3. Adult subjects who have BCVA of 75 letters or less in the study eye (20/32 Snellen equivalent) and Pediatric subjects who have a BCVA of 35 letters or better in the study eye (20/200 Snellen equivalent). 4. The study eye should have at least one well-demarcated area of atrophy with a minimum diameter of 300 microns, and total lesion size must add to less than or equal to ≤ 18 mm\^2 (approximately 7-disc areas). 5. Have detectable outer nuclear layer (ONL) in the macular region Phase 2/3 Exclusion Criteria (applicable for both adult and pediatric subjects): 1. Participation in ongoing antiretroviral therapy treatment. 2. Participation in any investigational therapy study or receipt of investigational treatment within 60 days prior to screening or 5 half-lives (whichever is longer). Any ophthalmic history of gene therapy, stem cell therapy, surgical implantation of prosthetic retinal chips, intravitreal or subretinal injections, or participation in an Alkeus ALK-001 study within the past 6 months. 3. Macular atrophy secondary to any disease other than Stargardt Disease (STGD). 4. Presence of genetic mutations that mimic Stargardt Disease like ELOVL4, or PROM1. 5. Contraindication to subretinal injection or use of anesthesia (local and/or general). Phase 1 was a multicenter, open-label, dose-ranging/dose escalation study. Enrollment is complete for Phase 1