The blockchain technology has brought a new tool which can change the way we make legal contracts. This tool is called “smart contracts”. Smart contracts are self-executing contracts which decrease the human intervention and the need for intermediaries for the execution of a contract. This thesis discusses whether smart contracts can really replace the traditional way we conclude legal contracts by comparing them with classic legal contracts based on the Principles of European Contract Law. It introduces a technical background about the blockchain and smart contract technology and questions whether smart contracts can be formed, valid, and executed as legal contracts. The thesis presents the legal challenges of smart contracts and finally concludes that smart contracts can and will replace the traditional way of making legal contracts in the distant future.