When deciding which database is best for React, there are several factors to consider. Scalability, data structure, ease of use, and cost are all important factors. MongoDB is a popular NoSQL database that is great for scalability and ease of use. MySQL is a popular open-source relational database that is great for scalability and powerful query language. PostgreSQL is an open-source object-relational database that combines the power of both relational and NoSQL databases. Firebase is a cloud-based database that is great for scalability and ease of use. Depending on the needs of your project, any of these databases can be the best choice for your React application.