In an era where digital identity and privacy are of paramount concern, traditional authentication systems often fall short in safeguarding user data from centralized breaches and surveillance. This thesis explores the design and implementation of a decentralized authentication framework that leverages blockchain technology and Zero-Knowledge Proofs (ZKPs) to enable secure and anonymous user login. By integrating Ethereum smart contracts, SHA256 hashing, and the ZoKrates ZKP-toolkit, the proposed system allows users to register with a public key and hashed password, and subsequently authenticate by proving knowledge of the password without revealing it. MetaMask is employed as a wallet interface for seamless interaction with the blockchain, offering a widely adopted and user-friendly interface for signing blockchain transactions. The proposed system is evaluated against conventional login systems based on metrics for security, and individually measured on the applications functionality. The results highlight the potential of ZKP-based authentication to enhance both security and user privacy, demonstrating a viable pathway toward more resilient digital identity systems.