This paper proposes a Secure and Scalable Cloud Healthcare Architecture with Aadhaar Authentication to enhance the efficiency, reliability, and security of healthcare services. The system employs authentication mechanisms provided by the Unique Identification Authority of India (UIDAI) to uniquely identify patients and eliminate duplication or identity fraud. Upon successful verification, encrypted electronic health records (EHRs) are stored and managed on a secure cloud platform, ensuring authorized access for healthcare providers. The architecture supports real-time data updates, interoperability across institutions, and electronic prescription generation. Advanced security mechanisms, including role-based access control and data encryption, ensure confidentiality and integrity. The proposed model delivers scalable, cost-effective, and patient-centric digital healthcare services.