Sharia-compliant fintech lending in Indonesia is intended to provide an alternative to conventional online lending. However, previous studies have largely addressed contractual structures, riba and gharar, or Sharia governance independently, leaving insufficient explanation of why contracts bearing Sharia-compliant labels may diverge from Sharia principles in practice. This article investigates the relationship between contractual validity, the implementation of DSN-MUI fatwas, and digital transaction mechanisms in determining the Sharia legitimacy of fintech lending. It employs normative legal research with qualitative analysis of primary legal materials, including DSN-MUI Fatwa No. 117/DSN-MUI/II/2018, relevant contractual fatwas, OJK Regulation No. 40 of 2024, and legislation governing electronic transactions and personal data. Relevant peer-reviewed literature supplements the legal analysis. The materials are examined deductively and compared across sources. The findings indicate that compliance with the essential elements and conditions of qardh, wakalah bil ujrah, murabahah, mudharabah, and musyarakah does not independently establish substantive Sharia compliance. Contractual legitimacy may be undermined when fees are directly linked to loan principal, partnership arrangements guarantee predetermined returns, or standardized electronic consent obscures material costs and risks. Although Sharia supervision, personal data protection, and ethical debt collection are not constitutive elements of contracts, they remain essential regulatory and consumer protection obligations. This study develops an integrated analytical framework connecting contractual validity, fee transparency, risk allocation, informed consent, and Sharia supervision. As the research does not involve direct observation of fintech platforms, its conclusions address the normative requirements governing contractual design rather than the actual operational practices of specific providers.